Were they structurally different (no voting maybe?), or just had a lot fewer people?
They were like email, except to the forum's address instead of someone else's personal address. Lots of RE: RE: RE: just like in email, lots of third-party 'forum' clients that parsed QWKmail packet downloads from the BBS and displayed threaded conversations. Moderators could remove posts from the forum, unlike usenet.
Structurally different. Take a look at the many Discourse groups around today. There's none of the same pile-on tendencies that Upvote based sites like HN, Reddit, and Lobste.rs has. There's nothing to gain by piling on usually, since there's no karma-with-the-crowd.
this threaded view so much better though. maybe sort by time instead of votes would be better. once you got through a few pages message boards got unreadable