I moderate comments lightly. This is a conscious choice I’ve made, for reasons I’ve explained here. However, I do have a few simple rules I ask commenters to follow, and I will not hesitate to 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.
No slurs. You know what the words are. Don’t use them. I don’t think I need to elaborate, this issue has never come up here to the best of my knowledge (if I’ve missed something please let me know). Though I may elaborate this rule in the future if needed.
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.
You can insult people, but comments that are only insults may get squished. I can be lax about this. If there’s some way I can squint at a comment and see an attempt at a substantive point, I may let it through. On the other hand, on the occasions when I have disemvoweled/banned people, this is most often the reason.
On top of this, I’d strongly encourage readers to be very careful with insults, and ask yourself if you have good reasons for them before posting. But I won’t judge disputes about whether your reasons are good via comment moderation. The only rule I’ll enforce is that you must at least try to say something of substance when you’re harsh on someone.
Creationism is a special case for purposes of this rule. Most of the time, I try to deal with creationists politely but firmly, telling them that the scientific consensus is overwhelming, and if they’re not willing to just take the scientists at their word then they should really make an effort to educate themselves better about the issue.
That said, I do not particularly care if, when people show up advocating creationism here, other commenters openly draw very negative conclusions about them without re-arguing the issue for the 300 millionth time. This isn’t merely because creationism is wrong beyond a reasonable doubt, but the evolution-creationism debate has been done to death, even more so that some of the other issues discussed on this blog. As such, I don’t particularly care about making my blog a place for debating the truth of evolution. (See here for the origins of my making creationism a special case.)
I’ve tried to be complete, but 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.
Don’t worry too much about this last one. It’s for extreme circumstances only. My general attitude towards comments is that if I dish it out I should be able to take it, and if a stupid fight breaks out in the comments other people can ignore it. I ask you to try not to be stupid, but I won’t try to enforce not being stupid.