A good norm to follow is to have comments (on torrents or in the forum) be about the topic at hand, not about other people. It's one thing to say "I don't like movie (or politician) XYZ," but quite another to say, "You're an idiot if you like movie (or politician) XYZ." There is, unfortunately, a lot of the latter going on, especially in the forum. It's probably a necessary evil, as the alternative would be to have our already overworked monitors policing every comment.
An important exception to the "principles, not personalities" rule would be giving thanks to someone for their efforts, such as a well-crafted torrent upload. Torrent quality seems to be drooping, so positive reinforcement of a job well done can benefit all of us.