I've added a "Commenting" link in the navigation bar at the top of this blog to remind people of my comment policies. They're pretty loose, but if you're wondering why a comment of yours wasn't approved, do some introspecting after you read the comment policy.
Each guideline is important, but failure to follow the one about insults probably irritates me the most, because there is nothing more boring than simple-minded personal insults. They belong in middle school, maybe, but not elsewhere. Like I say...
It's boring to insult people in a comment. Don't do it. Stand up for issues, ideas, concepts, and such that you feel need discussing. But don't insult other commenters, or anyone else. Criticize what someone says or does, not the person themselves.
Try to imagine you're in a person-to-person conversation. It is fine to say, "Hey, I disagree with what you're saying about ______. The way I see it is ______." It wouldn't be fine to say, "Hey, you're an idiot for saying _____. You should keep your mouth shut from now on."