What if some comments have a bimodal distribution (in how the community views them) between good and bad?

How do you recognize that, though? Your heuristic can't be "promotes comments with many downvotes" because the problem at hand is bad comments with many upvotes. If your heuristic is "promotes comments that others don't promote", how do you know you're not punishing someone for a minority viewpoint?

If the plan is for you to personally investigate promoters' promoting habits and make the call to take away the right, then I guess that would work but I don't know how it would scale. My skepticism is based on the idea that this could be done automatically.