Add filters when viewing a post's comments.

[NfNitLoop]

I recently implemented filtering for the user's feed.

Eventually, when there are many users on a server, a user might want to filter which comments are shown in reply to posts. For example:

• Include users I follow
• Include users followed by OP
• Include all (other) users on the server.

I'm not going to bother with this until I get some more users, though, and this actually becomes an issue.