I actually think this will help comment quality improve. You can definitely see the difference in the quality of comments on HN from a year ago to today. Just

I actually think this will help comment quality improve. You can definitely see the difference in the quality of comments on HN from a year ago to today. Just take a look on some articles on searchyc.com. I'm not saying that the quality today is any worse than the quality a year ago (it's very difficult to judge that metric), just the submissions and comments are different, which is to be expected of a growing community.