Comment quality here is still vastly higher than it is on most other sites frequented by programmers, designers or entrepreneurs, and higher than any other site (e.g. Wikipedia) of its size or larger. It's just really hard to maintain the quality of a site as big as the HN of 2011 when there are no significant barriers to participation by anyone with internet access and a basic command of the English language.
I humbly suggest that for the conversation to lead to HN's doing even better than HN has so far will require the participants in the conversation to verify that they are referring to the same thing when they write "comments that are (a) mean and/or (b) dumb", e.g., by the participant's providing actual examples (with the author's name removed) of comments they consider mean or dumb.