There's no doubt that some of the appeal of journals and weblogs is in the interaction and feedback, so why should we settle for anything less than mirroring?
Nobody talks back to an RSS feed... at least not yet.
And why only one bridge?! Why not mirror a weblog to multiple blogging / commenting systems?
Now if only it were easier to merge comments from multiple sources into one large conversation... that would be sweet!
(Yes, yes, trackback, I know. Will it work? Not like I want it to, and certainly not on LiveJournal yet. They have trackback on plogs.net, however, which is based on LJ's code. Infact, they've had it for 8 months. Their code is open source, too. So... what's LJ's excuse?!)