Negative reviews leading to death threats and rape threats? That’s what they’re claiming at the film site Rotten Tomatoes, where comments to reviews of the new Batman movie, “The Dark Knight Rises,” have been turned off, according to the Los Angeles Times.

The hateful rants show how difficult it can be to keep online conversations on track. I’m not a movie buff, and I rarely visit Rotten Tomatoes, so I don’t have an opinion regarding the way comments are monitored there. But editor-in-chief Matt Atchity told the Times that he had seven people moderating “Dark Knight” comments before he finally pulled the plug. Click here for Atchity’s message to readers.

Atchity also said his next step may be to integrate the commenting system with Facebook, which is probably a good idea. A lot of news sites have found that Facebook comments tend to be more civil, which no doubt is related to the mindset people are in — they’re checking in with their friends, they’re sharing pictures of their cats. And, of course, they are usually using their real names, complete with pictures of themselves.

Earlier this year, the New Haven Independent, a nonprofit news site widely admired for the way it uses comments to enhance its coverage, ran into a crisis that led it to shut down commenting for two weeks. When it reopened, it was with new, stricter policies. (See this and this.)

Engaging in a conversation with your users is necessary and useful. If they don’t feel like they’re part of your site, they’ll go somewhere else. But doing it right is not easy.