I guess NIP29 addresses this by declaring some first class kinds for topics and thread reply.

NIP72 suffered from the forced "moderation", limited implementations, and use of kind 1 for posts.

I am concerned by the bloat in NIP29 with all manner of rules for what relays should do for this NIP and restrictions on time of posted events. The way the relay is written seems to imply a customized relay implementation and front end. Maybe we just need the full plethora of common entities as kinds to mimic a traditional bulletin board.