In the left side bar, I have had a standing policy on comments for the past year. Here's what it says:

Keep it substantive, serious minded, on topic, and respectful.

Somewhat curiously, the only time I actually have to take action to enforce the comment policy is when a swarm of ardent faithful from PZ Myers' blog suddenly surges over here to complain about any criticism of PZ or any suggestion that diverts from the path of militant atheism. It's what physicist Chad Orzel describes in this post as the "screechy monkey" problem.