I don’t really like Discord, but it supports message pinning, threaded conversation, as well as a full blown discussion forum option for community channels. Your complaints seem to be more about the moderation of that specific community than Discord itself.

This was my exact experience as well. I’ll never know how Plex compares to Jellyfin because I immediately noped out when I ran into the account creation.

Frankly baffling to me that anyone with the wherewithal to self host thought that was okay.