Well, I would have deleted my "rabid," "aggressive," and "unsubstantive" comments, but apparently you've decided your users don't deserve the right to retract statements when they get off topic.
HN's window for comment deletion is fairly short because the threads are shared by the community. Letting people go back and delete comments after the fact would destroy the context necessary to understand them. So HN's policy has always been to leave most history intact even when the thread was regrettable. (I say 'most' because we do occasionally delete a comment when a user is worried about getting in trouble from it.)
