Eric Meyer writes about guiding a large [5,000+ member] mailing list community and how css-discuss is very much civil.

I also participate in the community as best I can, setting an example for how questions should be answered and list members should act. Of late, I’ve been too swamped to offer more than token participation on the list, which is why I just yesterday selected four list members to be moderators. They’ll be helping with administrivia, but more importantly, will be helping to keep things on-topic and civil, although I honestly don’t expect them to have to work very hard at that last part.

The founder’s influence is key. Back when the Rumor Forum was far more nascent, Bryan’s influence is what made it what it is. The heavily-involved users in 2002 are, in large part, still around, and they’re the ones that continue to guide the community as it gets far larger. As the RF is a variegated Web discussion board centered around a few themes, the topicality that Meyer speaks is out the window, and so we have, as a result, a pretty high volume for a far smaller group [~850 at present] of users. There’s no way that the RF—and the community at large—would never run as well as it does without our wonderful group of moderators/community leaders, which we call Bartenders, following the meme that our little forum is a lot like your corner pub.

In short, Eric is totally right: good leaders will make for a good community.