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I don't think trolling is much of a problem here. There is, however, a few individuals with extreme bias which tends to degrade conversation & debate. Additionally, there's a lack of respect towards those who have opinions which differ from 'your own' or the common view.
Aside of the silly "troll" and "fanboy" finger pointing here, things aren't that bad. Could be much worse for sure.
Lastly, I don't believe any 'karma' or vote system will do any good. People will always vote negatively for those they dislike or disagree with. They'll always vote positively for their 'friends' and those with like-opinions. This behavior has been proven a billion times over on a billion other forums.