FOr the record, LJ isn't quite as bad. For one, mmcirvin linked to this post from a more recent one.

Also, largely thanks to email notifications when I respond in other journals, I've continued discussions for a while, though only up to about a week. Even absent notifications, I've checked back on a post where I really really wanted to know where the discussion went, and you can even add watches to any post now. Useful when someone posts they'd like to have a group dinner but don't know where. It's not quite what 2ch's bumping system is though.