The Remote Permissions addon enables recipients of private posts to see who else has received the post. This can be beneficial on community servers where people may want to modify the way they speak depending on who can see their comments to the post.
Note that since Friendica is federated, the local hub may have posts that originated elsewhere. In that case, the addon has no way of knowing all the recipients of the post, and it must settle for finding out who else can see it on the local hub.
The hub admin can specify one of two behaviors for this addon: