Proposed solution: remove the karma penalty and do exactly the same thing we were doing before. That is, if someone is pretty sure that they will not benefit from reading the replies to a particular thread, they don't read them. No disincentives from posting such a reply needed. What is the problem with that system?
Edit: As of this edit, if one more person decides they don't like my comment, then no one can tell me why they don't like my comment without loosing 5 karma. One of many reasons the new system is terrible.
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).