I agree that comment sites require moderation, but HN makes every appearance of being community-moderated. The voting system is supposed to take care of the signal-to-noise ratio, and I think it does a pretty good job.
The moderation actions I am talking about, however, are unilateral (you can't even ask why), magical (you don't know it is happening), persistent (the account posts dead comments for a period of time, perhaps infinite), and arbitrary (the comments are not necessarily undesirable or contrary to the HN culture). These traits are bothersome to me, and to at least a few others. I think it warrants a discussion.