After reading my recent post on enabling comments a friend wrote me to ask about my thoughts on comment moderation mentioning that some have had success improving drastically the quality of discussion on a given site while acknowledging a high level of effort involved.
Moderation can be a pretty touchy subject, largely because people feel the right to free speech entitles them to say whatever they want to say whenever and wherever they want.
My favorite discussion of moderation came up on Ars Technica (which seems to come up frequently to me as close to the very model of how to conduct a civil online community) this past September. If you're interested in specifics, read Editor-in-Chief Ken Fisher's announcement post.
The gist is that Ars had an ever increasing flow of low-quality, immature, and asinine commenting over the course of the previous years or so (still in my opinion much higher quality than any other major site that covers similar subjects) and wanted to fix the problem. They annonuced a few hard line rules to give offenders ("trolls"--which they defined) a 24 timeout without warning on first infringements with automatic deletions of infringing posts if especially egregious or made by a brand new account (meaning chances are high the comment was made by a person joining for the sake of irritating others). The discussion they invited members to join in on was huge, hitting 929 comments on the story (I participated heavily and the discussion got me to finally become a paid member of the site), and let the staff gauge whether this was something the community wanted or not. The end result has been an Ars where I feel all the intelligent conversation has been left intact, including plenty of heated dissent, while spam posts and ad hominem attacks have been effectively reduced to nothing.
With all that in mind, my view is that good moderation is absolutely essential if you're going to foster civil discussion. Remove normal internet "FIRST" posts. Remove posts that attack a person instead of their argument. Remove negative comments that add nothing except negativity, but do not ever remove critical posts that justify their criticism. That last point is the most difficult one. It's the line that, when crossed, means you've gone from keeping things civil to quieting criticism. The point here is that a website which wants to become a community in and of itself has the responsibility to foster that community. At Ars that has been a major point of the website since it began. If you believe your own site is one that should be a community, you must make sure the comments on your site encourage quality discussion--and quality discussion generally includes quality criticism.
Moderation of a site's comments is essential when the comments are in any substantial volume unless you want to devolve into the types of worthless or offensive nonsense you get on YouTube (reading comments on 5 or 6 popular YouTube videos is an experiment you only need to try once--you'll never forget it). If you want your site to BE a community rather than to just take part in one, though, you have to tread carefully and make sure you're not crippling the quality of that community by discouraging those with founded dissent, even if it's a bit heated, from staying.