I'm guessing denounce is for bad faith behavior, not just low quality contributions. I think it's actually critical to have a way to represent this in a reputation system. It can be abused, but abuse of denouncement is grounds for denouncement, and being denounced by someone who is denounced by trusted people should carry little weight.

IDK about this implementation ...

OVER-Denouncing ought to be tracked, too, for a user's trustworthiness profile.