Flagging an entire thread by clicking 'troll' would help. The up/down voting tends to promote trolling, as the first controversial cliche is the top comment, having spawned a deep threaded conversation with lots of emotions and voting. A different symbol is needed. Something that makes people take pause and say, 'Is this a good subtopic of this link, or is it the exact debate anyone would have predicted?'

Put troll threads/comments at the bottom of the page, or hide them. Or use spam ratings to amplify users' votes who up vote non spam comments.

Short of that, add the ability to minimize entire threads.