Good Advice for Commenters:
I usually try to enforce our comment policy in part through warnings. If a commenter is crossing the line and being uncivil but I think there is hope that he'll change his tune, I try to respond by pointing out the uncivil comment and reminding the commenter that comments must be civil. A while back, Anon321 chimed in with some good advice about how to respond to such warnings:
  As should be clear to most commenters by now, the surest way to get banned is, after being warned, to quarrel with the warning, accuse the blogger of improper motives, whine about unequal standards, and generally try to turn the discussion towards the subject of banning.  If you get warned and don't think you deserved to, just accept the fact that you're playing in someone else's sandbox, say you're sorry, and/or let it go.
  That's good advice. After blogging for more than five years, and moderating comment threads for much of that time, I've developed a sense that there are two basic kinds of commenters who might be uncivil. The first is the commenter who recognizes the value of civility but sometimes gets excited or can be provoked. The second is the person who thinks civility is basically silly, and that we're all best off if we can speak as bluntly and directly as possible without mincing words. To the former person, a civility warning is a reminder to "play nice." To the latter, a warning is cover for censorship, evasion, and hiding from the deep truths that only harsh words voiced bravely by that commenter can communicate.

  My sense is that a warning tends to separate these two groups. The former group "gets it," and tries to comply. The latter group plays victim and tries to turn the warning into a debate on the precise standards for commenting and the fairness of the process. The trick is that the latter type of commenter is not someone we'd like to have commenting here. There a lot of blogs out there, and there are certainly places for such people to comment. But it's not our style, and therefore not the style of the small corner of the Internet that we're trying to host. As a result, playing the victim and trying to make the issue the banning (rather than the incivility) is usually a clear sign that the commenter is in the latter group: It ends up making it pretty likely that such a commenter will then be banned.

  Of course, a number of my co-bloggers have reacted to these problems by just giving up on comment threads entirely. I can't say I blame them: editing comments and responding to the objections of commenters about the editing process is really unhappy work. But I haven't entirely reached that point yet, so I thought I would flag anon321's good advice about how to respond (and how not to respond) if a blogger warns you to be civil.