I wholeheartedly agree with the necessity of finding ways of diverse opinions to rise. False-consensus effect is one of the hardest issues to overcome in the context of social media.
Still, the promotion of controversial comments sounds quite risky. I fear this would bipolarise the conversation online further. For example racistic and hateful comments tend to get a handful of positive and quite a lot of negative votes. If the system would prioritise these, the extreme opinions would certainly get more attention and the “silent majority” would appear even more silent.