I would imagine that a journal or community maps to a newsgroup, then you're presented with the entries as articles, and comments as articles with appropriate References pointing back to make it all threadable.

That would have been my thoughts, too.

Heh. It does map kind of nicely, and the "keeping track of read/unread comments" - and, for that matter, "finding new comments on old articles without having to subscribe explicitly to Every Single One" seem like really useful things.

Extra super would be bidirectional access, so that you could leave a comment by Following-Up to a news article... or post a new entry by posting a top-level one!