You'll also notice that people start making the same comments and having the same conversations over and over again. Instead of having an ongoing conversation about, say, space exploration, you have the same beginning of a discussion happening whenever the topic comes up, and then stopping before it really matures.
That's not to say that the comment section here is bad, but it's still worth paying attention to some of its drawbacks. Particularly because it shares the urgency and compulsive aspects that permeate a lot of current sites.
The only real addictive bit is the points system on HN. I'd be fine with that just going away. It wouldn't be the first time I've refreshed posts I've made repeatedly to see the tally go up.
The old style of forums didn't have the same kind of compulsive pressure, since you could always respond the next day/week/month and the topic would bump back up to the top of the post. If you don't respond on HN or Reddit quick enough, no one is going to see your comment. I frequent some sites that has the older system, and I'll find myself occasionally saying "This isn't that important; wait a few days and see if you feel like responding." But that's not really much of an option here - how many people are going to read your comment if you make it several days later?
And it wouldn't be hard to devise a system that actively discourages compulsive posting behavior. If you, say, had a web forum where everyone could only post once a week, you'd have much less of that urgency (and you'd get a discussion with more users, not just the fraction that habitually post everywhere).
It's been implied that this is an intentional means of keeping engagement low, as the quality of comments tends to diminish over time, while the likelihood of flamebait and spam increases as comment distance diverges from the root. This is also apparently the reason there are no notifications for new comments. I don't know if it's true or one of those features the community is reading too much meaning into, which only exists as it does because pg wasn't interested in expanding on it.
In any case, I really hope they consider adding more ways to sort the threads - sorting by time rather than karma would be very helpful. They could even keep the karma sort the default so no one else has to complain about the layout changing.
The fact that the 'shape' of the threads changes all the time does not help either (the way the messages are ordered, depending on the upvotes, the freshness, and whichever mysterious other criteria may be involved).
Conversations at a depth higher than 5 or 6 levels is also difficult to follow, so I think not many people read them, let alone take part in them (on Reddit, such deep threads even suffer a penalty twice, and the second one, which requires opening a new tab or window if you don't want to have to reload the whole page once you come back, is probably fatal to almost all of the readers).
(I won't tell how much I miss Usenet and newsreaders once more, I promise :-D )
I'm especially fond of the noprocrast feature. I don't know of any other site/app that will kick their users out if they use it for too long.