One idea: disconnect the visible down-votedness of a user's comment from a user's visible karma- which seems to upset people. I often see posts regarding 'why are you down voting my comment?'. Not allowing a post to get publicly, visibly, lower than 0 would prevent meta discussions about 'why'- even though the hidden negative score would move the actual comment down the publicly visible thread hierarchy.

Not showing downvoted scores on comments would never cause a user to exclaim 'why aren't you upvoting me?'

Disconnecting a user's visible karma from the hidden negative points a user acquires from negative/poor comments would be important for this idea to work well.