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).
An unintended side-effect: readers without credit/debit cards may find it harder to join the site. This disproportionately affects younger people, a demographic that may be more open to LW ideas.
Another unintended side-effect is that it may increase phyg pattern-matching. Now new recruits have to pay to join the site, and surely that money is being secretly funneled into EY's bank account.
That said, I think that on balance this is a good policy proposal. I also think that the similar proposal using phone verification is plausible, and doesn't run into the above two problems.
Heck, there's no pattern-matching about it. It will increase phyg.