@masimatutu this is a bit of self promotion here, but this is exactly what I want to with #nodebbActivityPub. Local only threads with the ability to two-way federate post content to followers. Implementors should be able to load the entirety of a NodeBB thread in their own native interfaces, and vice versa.
#Mastodon is the elephant in the room, and many implementors cater towards its idiosyncrasies but it needn't be that way.