Because the two styles are reddit style and bulletinBB style in my head. Those other three you mentioned are reddit style, too.
What makes the reddit style more similar to Twitter than to bulletin board, in your mind? And do we have a modern example of the bulletinBB style since phpBB?
Hacker news is reddit style, too (by far the closest of those listed). Somethingawful is an example of a BulletinBB style board in 2026.