> Comments should get more thoughtful and substantive, not less, as a topic gets more divisive.

> Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something.

Sure it does... Right up until the parent comment gets downvoted to oblivion, taking all subsequent responses out with it, leaving nothing potentially educational behind for anyone to learn from.

(Not a problem unique to HN by a longshot, but actually a shortcoming of nearly every discussion forum I've seen that allows downvoting.)