I have not had major complaints about comments, but to preempt any problems, some explicit policies:
1. Every person’s first comment is held for moderation, as a spam prevention tool. It is uncommon for me to take more than a few hours to see your comment and approve it. Of note: if you change your handle, your first comment with the new handle will be held as well.
2. Every comment with more than 6 links is held as well.
3. If you post a comment and don’t see it, even with “your comment is held for moderation,” it means it’s in the spamfilter. I will almost certainly rescue it on my own, but it will take a number of days; if you ask me to rescue it on Twitter or by email, it’ll happen a lot faster. I do not know what triggers the spamfilter, but it’s rare for legitimate comments to end up there – I believe it’s happened around twenty times in this blog’s history, out of ten thousand comments.
4. I do not remove comments unless they are spam, or duplicates. I do not edit other people’s comments except for technical reasons: for example, if your comment contains a broken link, and you then post the correct link below it, then I will consolidate the correct link into the original comment upon request.
5. You can’t edit your comments after the fact. The plugin for that as well as the plugin for comment preview do not exist in the free version of WordPress, unfortunately.
6. I do occasionally edit my own comments and posts after the fact. Usually it’s to fix typographical or grammatical errors, or (more in posts than comments) fixing broken links. Occasionally it’s to add new information or fix a mathematical or other error, and then I make it explicit that it’s an update; deprecated information is denoted with a strikethrough rather than deleted.