Many good discussions here, but its hard to keep track of through 'thread' or 'comments' feature. Why can't HN send an email everytime someone responds to a thread I am part of, or to a post that I made? Apparently the only posts that gets more discussion are the controversial ones (like the currently hot 'Mike Arrington got pissed!'). I would like to see more activity on other tech topics as well, and email will certainly help.
For many people, the only way this would be sustainable would be to offer digests. Being emailed "everytime [sic] someone responds to a thread I am a part of, or a post I made" would be a complete nightmare.
Alternatively, you could use BackType Subscriptions to do this, as well as follow threads you're not participating in:<p><a href="http://www.backtype.com/subscriptions" rel="nofollow">http://www.backtype.com/subscriptions</a><p>We have a bookmarklet too -- so adding subscriptions can be less painful.