I notice that nobody here is playing devil's advocate, so allow me. What was wrong with the site beforehand? Sure the comments have a mob feel to them sometimes, but that's just something a social anything app has to deal with.
Over all, I like the comments on HN much more than say reddit or digg by far. Plus, I've never seen a community that responds so well to criticism as this one does.
Social anything apps don't have to turn into mobs. Twitter's not a mob. Facebook's not a mob. Most large forums don't turn into mobs. In fact, forums, because they don't allow for comment voting, usually are much better against sensationalist postings because you understand every post is a user's opinion and not the vox populi.
Over all, I like the comments on HN much more than say reddit or digg by far. Plus, I've never seen a community that responds so well to criticism as this one does.