diff --git a/include/api.php b/include/api.php
index 6f8c952475..f1a8e5ee94 100644
--- a/include/api.php
+++ b/include/api.php
@@ -1559,7 +1559,7 @@ function api_search($type)
 		$params['group_by'] = ['uri-id'];
 	} else {
 		$condition = ["`id` > ?
-			" . ($exclude_replies ? " AND `id` = `parent` " : ' ') . "
+			" . ($exclude_replies ? " AND `gravity` = " . GRAVITY_PARENT : ' ') . "
 			AND (`uid` = 0 OR (`uid` = ? AND NOT `global`))
 			AND `body` LIKE CONCAT('%',?,'%')",
 			$since_id, api_user(), $_REQUEST['q']];
@@ -3028,7 +3028,7 @@ function api_format_item($item, $type = "json", $status_user = null, $author_use
 	$retweeted_item = [];
 	$quoted_item = [];
 
-	if ($item["id"] == $item["parent"]) {
+	if ($item['gravity'] == GRAVITY_PARENT) {
 		$body = $item['body'];
 		$retweeted_item = api_share_as_retweet($item);
 		if ($body != $item['body']) {
diff --git a/include/conversation.php b/include/conversation.php
index eb5e95d6db..b163184af9 100644
--- a/include/conversation.php
+++ b/include/conversation.php
@@ -671,7 +671,7 @@ function conversation(App $a, array $items, $mode, $update, $preview = false, $o
 
 				$item['pagedrop'] = $page_dropping;
 
-				if ($item['id'] == $item['parent']) {
+				if ($item['gravity'] == GRAVITY_PARENT) {
 					$item_object = new Post($item);
 					$conv->addParent($item_object);
 				}
@@ -948,7 +948,7 @@ function builtin_activity_puller($item, &$conv_responses) {
 				return;
 		}
 
-		if (!empty($item['verb']) && DI::activity()->match($item['verb'], $verb) && ($item['id'] != $item['parent'])) {
+		if (!empty($item['verb']) && DI::activity()->match($item['verb'], $verb) && ($item['gravity'] != GRAVITY_PARENT)) {
 			$author = ['uid' => 0, 'id' => $item['author-id'],
 				'network' => $item['author-network'], 'url' => $item['author-link']];
 			$url = Contact::magicLinkByContact($author);
@@ -1218,7 +1218,7 @@ function get_item_children(array &$item_list, array $parent, $recursive = true)
 {
 	$children = [];
 	foreach ($item_list as $i => $item) {
-		if ($item['id'] != $item['parent']) {
+		if ($item['gravity'] != GRAVITY_PARENT) {
 			if ($recursive) {
 				// Fallback to parent-uri if thr-parent is not set
 				$thr_parent = $item['thr-parent'];
@@ -1366,7 +1366,7 @@ function conv_sort(array $item_list, $order)
 
 	// Extract the top level items
 	foreach ($item_array as $item) {
-		if ($item['id'] == $item['parent']) {
+		if ($item['gravity'] == GRAVITY_PARENT) {
 			$parents[] = $item;
 		}
 	}
diff --git a/mod/display.php b/mod/display.php
index a06d8a7239..d3c0e02499 100644
--- a/mod/display.php
+++ b/mod/display.php
@@ -54,7 +54,7 @@ function display_init(App $a)
 	$item = null;
 	$item_user = local_user();
 
-	$fields = ['id', 'parent', 'author-id', 'body', 'uid', 'guid'];
+	$fields = ['id', 'parent', 'author-id', 'body', 'uid', 'guid', 'gravity'];
 
 	// If there is only one parameter, then check if this parameter could be a guid
 	if ($a->argc == 2) {
@@ -101,12 +101,12 @@ function display_init(App $a)
 	}
 
 	if (!empty($_SERVER['HTTP_ACCEPT']) && strstr($_SERVER['HTTP_ACCEPT'], 'application/atom+xml')) {
-		Logger::log('Directly serving XML for id '.$item["id"], Logger::DEBUG);
-		displayShowFeed($item["id"], false);
+		Logger::log('Directly serving XML for id '.$item['id'], Logger::DEBUG);
+		displayShowFeed($item['id'], false);
 	}
 
-	if ($item["id"] != $item["parent"]) {
-		$parent = Item::selectFirstForUser($item_user, $fields, ['id' => $item["parent"]]);
+	if ($item['gravity'] != GRAVITY_PARENT) {
+		$parent = Item::selectFirstForUser($item_user, $fields, ['id' => $item['parent']]);
 		$item = $parent ?: $item;
 	}
 
@@ -205,8 +205,8 @@ function display_content(App $a, $update = false, $update_uid = 0)
 				$condition = ['guid' => $a->argv[1], 'uid' => local_user()];
 				$item = Item::selectFirstForUser(local_user(), $fields, $condition);
 				if (DBA::isResult($item)) {
-					$item_id = $item["id"];
-					$item_parent = $item["parent"];
+					$item_id = $item['id'];
+					$item_parent = $item['parent'];
 					$item_parent_uri = $item['parent-uri'];
 				}
 			}
@@ -214,8 +214,8 @@ function display_content(App $a, $update = false, $update_uid = 0)
 			if (($item_parent == 0) && remote_user()) {
 				$item = Item::selectFirst($fields, ['guid' => $a->argv[1], 'private' => Item::PRIVATE, 'origin' => true]);
 				if (DBA::isResult($item) && Contact::isFollower(remote_user(), $item['uid'])) {
-					$item_id = $item["id"];
-					$item_parent = $item["parent"];
+					$item_id = $item['id'];
+					$item_parent = $item['parent'];
 					$item_parent_uri = $item['parent-uri'];
 				}
 			}
@@ -224,8 +224,8 @@ function display_content(App $a, $update = false, $update_uid = 0)
 				$condition = ['private' => [Item::PUBLIC, Item::UNLISTED], 'guid' => $a->argv[1], 'uid' => 0];
 				$item = Item::selectFirstForUser(local_user(), $fields, $condition);
 				if (DBA::isResult($item)) {
-					$item_id = $item["id"];
-					$item_parent = $item["parent"];
+					$item_id = $item['id'];
+					$item_parent = $item['parent'];
 					$item_parent_uri = $item['parent-uri'];
 				}
 			}
diff --git a/mod/item.php b/mod/item.php
index ad3351dd4a..6671d94393 100644
--- a/mod/item.php
+++ b/mod/item.php
@@ -119,7 +119,7 @@ function item_post(App $a) {
 			// The URI and the contact is taken from the direct parent which needn't to be the top parent
 			$thr_parent_uri = $toplevel_item['uri'];
 
-			if ($toplevel_item['id'] != $toplevel_item['parent']) {
+			if ($toplevel_item['gravity'] != GRAVITY_PARENT) {
 				$toplevel_item = Item::selectFirst([], ['id' => $toplevel_item['parent']]);
 			}
 		}
diff --git a/mod/network.php b/mod/network.php
index 433d4079c1..16fde6c351 100644
--- a/mod/network.php
+++ b/mod/network.php
@@ -709,7 +709,7 @@ function networkThreadedView(App $a, $update, $parent)
 			}
 			if ($order === 'post') {
 				// Only show toplevel posts when updating posts in this order mode
-				$sql_extra4 .= " AND `item`.`id` = `item`.`parent`";
+				$sql_extra4 .= " AND `item`.`gravity` = " . GRAVITY_PARENT;
 			}
 		}
 
diff --git a/mod/photos.php b/mod/photos.php
index 7a647e06b9..7b74a39dd8 100644
--- a/mod/photos.php
+++ b/mod/photos.php
@@ -1456,7 +1456,7 @@ function photos_content(App $a)
 
 					if (($activity->match($item['verb'], Activity::LIKE) ||
 					     $activity->match($item['verb'], Activity::DISLIKE)) &&
-					    ($item['id'] != $item['parent'])) {
+					    ($item['gravity'] != GRAVITY_PARENT)) {
 						continue;
 					}
 
diff --git a/mod/ping.php b/mod/ping.php
index 168b508ea0..73e759107b 100644
--- a/mod/ping.php
+++ b/mod/ping.php
@@ -467,13 +467,13 @@ function ping_get_notifications($uid)
 
 			if ($notification["visible"]
 				&& !$notification["deleted"]
-				&& empty($result[$notification["parent"]])
+				&& empty($result[$notification['parent']])
 			) {
 				// Should we condense the notifications or show them all?
 				if (DI::pConfig()->get(local_user(), 'system', 'detailed_notif')) {
 					$result[$notification["id"]] = $notification;
 				} else {
-					$result[$notification["parent"]] = $notification;
+					$result[$notification['parent']] = $notification;
 				}
 			}
 		}
diff --git a/src/Factory/Notification/Notification.php b/src/Factory/Notification/Notification.php
index 990d274a01..cedc0ad656 100644
--- a/src/Factory/Notification/Notification.php
+++ b/src/Factory/Notification/Notification.php
@@ -95,11 +95,11 @@ class Notification extends BaseFactory
 			$item['author-avatar'] = $item['contact-avatar'];
 		}
 
-		$item['label'] = (($item['id'] == $item['parent']) ? 'post' : 'comment');
+		$item['label'] = (($item['gravity'] == GRAVITY_PARENT) ? 'post' : 'comment');
 		$item['link']  = $this->baseUrl->get(true) . '/display/' . $item['parent-guid'];
 		$item['image'] = Proxy::proxifyUrl($item['author-avatar'], false, Proxy::SIZE_MICRO);
 		$item['url']   = $item['author-link'];
-		$item['text']  = (($item['id'] == $item['parent'])
+		$item['text']  = (($item['gravity'] == GRAVITY_PARENT)
 			? $this->l10n->t("%s created a new post", $item['author-name'])
 			: $this->l10n->t("%s commented on %s's post", $item['author-name'], $item['parent-author-name']));
 		$item['when']  = DateTimeFormat::local($item['created'], 'r');
diff --git a/src/Model/Item.php b/src/Model/Item.php
index 6b48acf4cb..a6036e6bdb 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -1047,7 +1047,7 @@ class Item
 		$fields = ['id', 'uri', 'uri-id', 'uid', 'parent', 'parent-uri', 'origin',
 			'deleted', 'file', 'resource-id', 'event-id', 'attach',
 			'verb', 'object-type', 'object', 'target', 'contact-id',
-			'icid', 'psid'];
+			'icid', 'psid', 'gravity'];
 		$item = self::selectFirst($fields, ['id' => $item_id]);
 		if (!DBA::isResult($item)) {
 			Logger::info('Item not found.', ['id' => $item_id]);
@@ -1138,7 +1138,7 @@ class Item
 		//}
 
 		// If it's the parent of a comment thread, kill all the kids
-		if ($item['id'] == $item['parent']) {
+		if ($item['gravity'] == GRAVITY_PARENT) {
 			self::markForDeletion(['parent' => $item['parent'], 'deleted' => false], $priority);
 		}
 
@@ -1494,7 +1494,7 @@ class Item
 				}
 			}
 
-			$item["parent"]        = $parent['id'];
+			$item['parent']        = $parent['id'];
 			$item["deleted"]       = $parent['deleted'];
 			$item["allow_cid"]     = $parent['allow_cid'];
 			$item['allow_gid']     = $parent['allow_gid'];
@@ -1529,8 +1529,8 @@ class Item
 
 			// If its a post that originated here then tag the thread as "mention"
 			if ($item['origin'] && $item['uid']) {
-				DBA::update('thread', ['mention' => true], ['iid' => $item["parent"]]);
-				Logger::info('tagged thread as mention', ['parent' => $item["parent"], 'uid' => $item['uid']]);
+				DBA::update('thread', ['mention' => true], ['iid' => $item['parent']]);
+				Logger::info('tagged thread as mention', ['parent' => $item['parent'], 'uid' => $item['uid']]);
 			}
 
 			// Update the contact relations
@@ -2246,7 +2246,7 @@ class Item
 		}
 
 		// Is it a toplevel post?
-		if ($item['id'] == $item['parent']) {
+		if ($item['gravity'] == GRAVITY_PARENT) {
 			self::addShadow($itemid);
 			return;
 		}
@@ -2544,7 +2544,7 @@ class Item
 
 		if (!$mention) {
 			if (($community_page || $prvgroup) &&
-				  !$item['wall'] && !$item['origin'] && ($item['id'] == $item['parent'])) {
+				  !$item['wall'] && !$item['origin'] && ($item['gravity'] == GRAVITY_PARENT)) {
 				Logger::info('Delete private group/communiy top-level item without mention', ['id' => $item_id, 'guid'=> $item['guid']]);
 				DBA::delete('item', ['id' => $item_id]);
 				return true;
@@ -2845,7 +2845,7 @@ class Item
 			return;
 		}
 
-		$condition = ["`uid` = ? AND NOT `deleted` AND `id` = `parent` AND `gravity` = ?",
+		$condition = ["`uid` = ? AND NOT `deleted` AND `gravity` = ?",
 			$uid, GRAVITY_PARENT];
 
 		/*
@@ -3227,9 +3227,9 @@ class Item
 			return DI::l10n()->t('event');
 		} elseif (!empty($item['resource-id'])) {
 			return DI::l10n()->t('photo');
-		} elseif (!empty($item['verb']) && $item['verb'] !== Activity::POST) {
+		} elseif ($item['gravity'] == GRAVITY_ACTIVITY) {
 			return DI::l10n()->t('activity');
-		} elseif ($item['id'] != $item['parent']) {
+		} elseif ($item['gravity'] == GRAVITY_COMMENT) {
 			return DI::l10n()->t('comment');
 		}
 
diff --git a/src/Object/Post.php b/src/Object/Post.php
index 8488df000f..1ca02873d7 100644
--- a/src/Object/Post.php
+++ b/src/Object/Post.php
@@ -214,7 +214,7 @@ class Post
 			$pinned = DI::l10n()->t('pinned item');
 		}
 
-		if ($origin && ($item['id'] != $item['parent']) && ($item['network'] == Protocol::ACTIVITYPUB)) {
+		if ($origin && ($item['gravity'] != GRAVITY_PARENT) && ($item['network'] == Protocol::ACTIVITYPUB)) {
 			// ActivityPub doesn't allow removal of remote comments
 			$delete = DI::l10n()->t('Delete locally');
 		} else {
diff --git a/src/Protocol/DFRN.php b/src/Protocol/DFRN.php
index 9ca23f1dcb..54e44f5b99 100644
--- a/src/Protocol/DFRN.php
+++ b/src/Protocol/DFRN.php
@@ -1059,7 +1059,7 @@ class DFRN
 
 		if ($item['object-type'] != "") {
 			XML::addElement($doc, $entry, "activity:object-type", $item['object-type']);
-		} elseif ($item['id'] == $item['parent']) {
+		} elseif ($item['gravity'] == GRAVITY_PARENT) {
 			XML::addElement($doc, $entry, "activity:object-type", Activity\ObjectType::NOTE);
 		} else {
 			XML::addElement($doc, $entry, "activity:object-type", Activity\ObjectType::COMMENT);
@@ -2110,7 +2110,7 @@ class DFRN
 				$author = DBA::selectFirst('contact', ['name', 'thumb', 'url'], ['id' => $item['author-id']]);
 
 				$parent = Item::selectFirst(['id'], ['uri' => $item['parent-uri'], 'uid' => $importer["importer_uid"]]);
-				$item["parent"] = $parent['id'];
+				$item['parent'] = $parent['id'];
 
 				// send a notification
 				notification(
@@ -2129,7 +2129,7 @@ class DFRN
 					"verb"         => $item["verb"],
 					"otype"        => "person",
 					"activity"     => $verb,
-					"parent"       => $item["parent"]]
+					"parent"       => $item['parent']]
 				);
 			}
 		}
@@ -2634,7 +2634,7 @@ class DFRN
 		}
 
 		$condition = ['uri' => $uri, 'uid' => $importer["importer_uid"]];
-		$item = Item::selectFirst(['id', 'parent', 'contact-id', 'file', 'deleted'], $condition);
+		$item = Item::selectFirst(['id', 'parent', 'contact-id', 'file', 'deleted', 'gravity'], $condition);
 		if (!DBA::isResult($item)) {
 			Logger::log("Item with uri " . $uri . " for user " . $importer["importer_uid"] . " wasn't found.", Logger::DEBUG);
 			return;
@@ -2646,13 +2646,13 @@ class DFRN
 		}
 
 		// When it is a starting post it has to belong to the person that wants to delete it
-		if (($item['id'] == $item['parent']) && ($item['contact-id'] != $importer["id"])) {
+		if (($item['gravity'] == GRAVITY_PARENT) && ($item['contact-id'] != $importer["id"])) {
 			Logger::log("Item with uri " . $uri . " don't belong to contact " . $importer["id"] . " - ignoring deletion.", Logger::DEBUG);
 			return;
 		}
 
 		// Comments can be deleted by the thread owner or comment owner
-		if (($item['id'] != $item['parent']) && ($item['contact-id'] != $importer["id"])) {
+		if (($item['gravity'] != GRAVITY_PARENT) && ($item['contact-id'] != $importer["id"])) {
 			$condition = ['id' => $item['parent'], 'contact-id' => $importer["id"]];
 			if (!Item::exists($condition)) {
 				Logger::log("Item with uri " . $uri . " wasn't found or mustn't be deleted by contact " . $importer["id"] . " - ignoring deletion.", Logger::DEBUG);
diff --git a/src/Protocol/Diaspora.php b/src/Protocol/Diaspora.php
index 243550862b..c4e7d9fb87 100644
--- a/src/Protocol/Diaspora.php
+++ b/src/Protocol/Diaspora.php
@@ -1517,7 +1517,7 @@ class Diaspora
 	private static function parentItem($uid, $guid, $author, array $contact)
 	{
 		$fields = ['id', 'parent', 'body', 'wall', 'uri', 'guid', 'private', 'origin',
-			'author-name', 'author-link', 'author-avatar',
+			'author-name', 'author-link', 'author-avatar', 'gravity',
 			'owner-name', 'owner-link', 'owner-avatar'];
 		$condition = ['uid' => $uid, 'guid' => $guid];
 		$item = Item::selectFirst($fields, $condition);
@@ -2164,8 +2164,8 @@ class Diaspora
 		$datarray["changed"] = $datarray["created"] = $datarray["edited"] = DateTimeFormat::utcNow();
 
 		// like on comments have the comment as parent. So we need to fetch the toplevel parent
-		if ($parent_item["id"] != $parent_item["parent"]) {
-			$toplevel = Item::selectFirst(['origin'], ['id' => $parent_item["parent"]]);
+		if ($parent_item['gravity'] != GRAVITY_PARENT) {
+			$toplevel = Item::selectFirst(['origin'], ['id' => $parent_item['parent']]);
 			$origin = $toplevel["origin"];
 		} else {
 			$origin = $parent_item["origin"];
@@ -2891,7 +2891,7 @@ class Diaspora
 			}
 
 			// Fetch the parent item
-			$parent = Item::selectFirst(['author-link'], ['id' => $item["parent"]]);
+			$parent = Item::selectFirst(['author-link'], ['id' => $item['parent']]);
 
 			// Only delete it if the parent author really fits
 			if (!Strings::compareLink($parent["author-link"], $contact["url"]) && !Strings::compareLink($item["author-link"], $contact["url"])) {
@@ -2901,7 +2901,7 @@ class Diaspora
 
 			Item::markForDeletion(['id' => $item['id']]);
 
-			Logger::log("Deleted target ".$target_guid." (".$item["id"].") from user ".$item["uid"]." parent: ".$item["parent"], Logger::DEBUG);
+			Logger::log("Deleted target ".$target_guid." (".$item["id"].") from user ".$item["uid"]." parent: ".$item['parent'], Logger::DEBUG);
 		}
 
 		return true;
@@ -3870,9 +3870,9 @@ class Diaspora
 			return $result;
 		}
 
-		$toplevel_item = Item::selectFirst(['guid', 'author-id', 'author-link'], ['id' => $item["parent"], 'parent' => $item["parent"]]);
+		$toplevel_item = Item::selectFirst(['guid', 'author-id', 'author-link'], ['id' => $item['parent'], 'parent' => $item['parent']]);
 		if (!DBA::isResult($toplevel_item)) {
-			Logger::error('Missing parent conversation item', ['parent' => $item["parent"]]);
+			Logger::error('Missing parent conversation item', ['parent' => $item['parent']]);
 			return false;
 		}
 
@@ -4066,7 +4066,7 @@ class Diaspora
 
 		$msg_type = "retraction";
 
-		if ($item['id'] == $item['parent']) {
+		if ($item['gravity'] == GRAVITY_PARENT) {
 			$target_type = "Post";
 		} elseif (in_array($item["verb"], [Activity::LIKE, Activity::DISLIKE])) {
 			$target_type = "Like";
diff --git a/src/Protocol/OStatus.php b/src/Protocol/OStatus.php
index 4cb27956ba..24decc000e 100644
--- a/src/Protocol/OStatus.php
+++ b/src/Protocol/OStatus.php
@@ -1675,7 +1675,7 @@ class OStatus
 	 */
 	private static function reshareEntry(DOMDocument $doc, array $item, array $owner, $repeated_guid, $toplevel)
 	{
-		if (($item["id"] != $item["parent"]) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
+		if (($item['gravity'] != GRAVITY_PARENT) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
 			Logger::log("OStatus entry is from author ".$owner["url"]." - not from ".$item["author-link"].". Quitting.", Logger::DEBUG);
 		}
 
@@ -1740,7 +1740,7 @@ class OStatus
 	 */
 	private static function likeEntry(DOMDocument $doc, array $item, array $owner, $toplevel)
 	{
-		if (($item["id"] != $item["parent"]) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
+		if (($item['gravity'] != GRAVITY_PARENT) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
 			Logger::log("OStatus entry is from author ".$owner["url"]." - not from ".$item["author-link"].". Quitting.", Logger::DEBUG);
 		}
 
@@ -1824,7 +1824,7 @@ class OStatus
 	 */
 	private static function followEntry(DOMDocument $doc, array $item, array $owner, $toplevel)
 	{
-		$item["id"] = $item["parent"] = 0;
+		$item["id"] = $item['parent'] = 0;
 		$item["created"] = $item["edited"] = date("c");
 		$item["private"] = Item::PRIVATE;
 
@@ -1889,7 +1889,7 @@ class OStatus
 	 */
 	private static function noteEntry(DOMDocument $doc, array $item, array $owner, $toplevel, $feed_mode)
 	{
-		if (($item["id"] != $item["parent"]) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
+		if (($item['gravity'] != GRAVITY_PARENT) && (Strings::normaliseLink($item["author-link"]) != Strings::normaliseLink($owner["url"]))) {
 			Logger::log("OStatus entry is from author ".$owner["url"]." - not from ".$item["author-link"].". Quitting.", Logger::DEBUG);
 		}
 
@@ -2021,7 +2021,7 @@ class OStatus
 		$mentioned = [];
 
 		if (($item['parent'] != $item['id']) || ($item['parent-uri'] !== $item['uri']) || (($item['thr-parent'] !== '') && ($item['thr-parent'] !== $item['uri']))) {
-			$parent = Item::selectFirst(['guid', 'author-link', 'owner-link'], ['id' => $item["parent"]]);
+			$parent = Item::selectFirst(['guid', 'author-link', 'owner-link'], ['id' => $item['parent']]);
 			$parent_item = (($item['thr-parent']) ? $item['thr-parent'] : $item['parent-uri']);
 
 			$thrparent = Item::selectFirst(['guid', 'author-link', 'owner-link', 'plink'], ['uid' => $owner["uid"], 'uri' => $parent_item]);
@@ -2047,7 +2047,7 @@ class OStatus
 			XML::addElement($doc, $entry, "link", "", $attributes);
 		}
 
-		if (!$feed_mode && (intval($item["parent"]) > 0)) {
+		if (!$feed_mode && (intval($item['parent']) > 0)) {
 			$conversation_href = $conversation_uri = str_replace('/objects/', '/context/', $item['parent-uri']);
 
 			if (isset($parent_item)) {
@@ -2066,7 +2066,7 @@ class OStatus
 
 			$attributes = [
 					"href" => $conversation_href,
-					"local_id" => $item["parent"],
+					"local_id" => $item['parent'],
 					"ref" => $conversation_uri];
 
 			XML::addElement($doc, $entry, "ostatus:conversation", $conversation_uri, $attributes);