You've simply assumed that engaged users are less likely to vote up fatuous vitriol. That remains to be shown and I'm skeptical.
https://news.ycombinator.com/item?id=5936055
To be clear: what he's saying in this thread seems to support the idea of a karma-limited feature for showing comments. The score (not the content) on a comment would have been negative; the comment, in context, was a superficial negative comment that commanded the top spot on a thread.