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).
On prior forums I have been on, attempts to split into a only some posters and all posters forums have ended badly.
When there are enouph high class posters, everything goes into the high class forum and the open forum collapses leaving no worthwhile "in" for new users. When there are too few high class users, everyone double posts to both forums in order to get discussion and you wind up with a functional 1 forum system except with lots of links and more burden and top level menus.
I have not seen an open / closed forum system with exactly the goldilocks number of high class users to maintain stable equilibria in both forums.