In the past, I’ve tended to moderate comments fairly lightly, for reasons I’ve explained here. However, recently I’ve decided to get stricter. I will not hesitate to delete or disemvowel comments that violate them and ban commenters who violate them repeatedly.
Disqus accounts and guest comments: It should go without saying that sockpuppetry and impersonating other commenters is unacceptable. In fact, generally speaking I prefer that people use a single account to comment here, even if you have multiple accounts (and even though I recognize there are innocent reasons for sometimes innocent reasons for sometimes using one account, sometimes using another, including just forgetting which one you were logged in on).
Guest comments (comments made without registering for any kind of account) are allowed, but will require me to approve your comment first. Again, picking a single handle for all your guest comments and sticking with it is preferred. If I come to recognize a guest handle and know you’re not going to be breaking any of the other rules, I’ll “whitelist” you to have your guest comments appear without approval.
Don’t be a jerk for no good reason. I don’t believe in being polite 100% of the time, but if I think you’re being a jerk for no good reason, your comment will get squished. This is a change from the past, when I’ve been afraid of the mere appearance of arbitrariness in how I moderate comments. I no longer care.
Respect other people’s privacy. I agree exactly with PZ Myers on this issue: “It takes very bad behavior to get me to expose a poster’s identity; you aren’t allowed to do it at all. Posting phone numbers or addresses, unveiling real names beschind pseudonyms… the banhammer comes down, along with comment deletion.” This is an exception to the rule that I will generally disemvowel, rather than delete, first offenses.
No spam. Personally, I consider “spam” to include comments that don’t really have anything to do with the discussion, and serve only to promote your own stuff. You can link to or quote yourself if it’s relevant. And you can disagree with me about what parts of “the discussion” (whatever that is for a particular post) are important. But if the relevance to a post is really, really, shaky, you may get disemvowelled.
I reserve the right to moderate comments, or even ban people, for other reasons. I’m adding this one mainly because unexpected and even downright weird situations can occur that don’t fall under any of the above. Since I can’t anticipate every such situation, I’m making this a general warning.
In my experience, “downright weird” comes up less often than general “being a jerk for no reason,” but again I’m not afraid to have people think I’m being arbitrary.