I find it interesting how Tumblr can frame a reply as a post, a different highlighting of the fractal flow of conversation, though ain't nobody got time for that, imo. I'll stick with plain ol' threaded HN/Reddit (though I think I remember finding a parent post for deep links to HN annoyingly unintuitive).

edit; ah, it has that - http://try.discourse.org/t/yo-dawg-heard-you-like-replies-so....

I like the new UX ideas. I'm wondering if instances will be able to federate, and the 'front page term[/hashtag](s)' for the discussion area of a certain website on a topic could be framed differently.

Some topics are going to get to crazy posting speed. Watching Reddit posts with new set on isn't that fun. An IRC/Jabber MUC format would be good for times, and Facebook autoupdates its newsfeed anyway. An IM system with text (and at least url) post and their replies upvoted, and maybe filtered in some tiling window like fashion?

There's my half-baked idea for the evening!