There are also a lot of HNers (myself included) who will upvote any comments they see that they think are unfairly downvoted, whether they agree or disagree wit

There are also a lot of HNers (myself included) who will upvote any comments they see that they think are unfairly downvoted, whether they agree or disagree with the comment. It creates a pretty good balancing effect. The end result is that comments that stay downvoted after having a decent number of eyeballs on them seem to usually deserve it. A possible exception are hyper-contentious issues (Israel/Palestine for example), where the upvote/downvote count is just a reflection of which tribe has greater numbers on HN.