If your website has an active community, you may want to include your readers in the process of moderating inappropriate or spam comments. Many websites have features that allow their readers to flag or report noisy comments, which can make your life a little bit easier; other, more sophisticated systems are used by websites like Hacker News and Slashdot, where readers use a voting system to filter out unproductive comments. Although this won’t get rid of spam and trolls entirely, it will discourage bad behavior as useless comments become less likely to be seen.

via Content Strategy Tips for Managing Comments on Your Website.