The recent implementation of a -5 karma penalty for replying to comments that are at -3 or below has clearly met with some disagreement and controversy. See http://lesswrong.com/r/discussion/lw/eb9/meta_karma_for_last_30_days/7aon . However, at the same time, it seems that Eliezer's observation that trolling and related problems have over time gotten worse here may be correct. It may be that this an inevitable consequence of growth, but it may be that it can be handled or reduced with some solution or set of solutions. I'm starting this discussion thread for people to propose possible solutions. To minimize anchoring bias and related problems, I'm not going to include my ideas in this header but in a comment below. People should think about the problem before reading proposed solutions (again to minimize anchoring issues).
This would be an improvement since then one's karma would still remain in principle obtainable by summing the karma of all one's comments and posts. But then, why have the arbitrary numbers -3 and -5? Wouldn't it be better if a reply to a negatively rated comment started at the same karma as the parent comment? Smooth rewarding schemes usually work better than those with thresholds and steps.
(I still don't support karma penalties for replies in general.)
Reading troll comments has negative utility. Replying to a troll means causing that loss of utility to each reader who wants to read the reply (times the probability that they read the troll when reading the reply). Perhaps giving the reply rating the same rating as the troll would be a more equitable utility cost to karma.