This doesn't address the flaws of the karma system. Karma goes astray as both an incentive and a measurement primarily because karma inflation distorts incenti

This doesn't address the flaws of the karma system. Karma goes astray as both an incentive and a measurement primarily because karma inflation distorts incentives; more users and more voting dilutes the impact of down voting, leading people to judge comment scores relative to other comments which makes genuine trouble makers harder to spot in the trends. Hacker News appears to be the same as Reddit with regard to how people treat karma, which seems to have been encouraged by the adoption of private karma: thermostat voting has gone down (but I remember offhand a comment by pg that this has not influenced scores, if this is correct the only significance is that down votes are now a much better data point should pg ever want a more sophisticated ranking system), but it has exacerbated comment relativity, doubly so because rather than using comment scores to only order comments, HN also obscures posts with a score lower than one. Disclosure: Community moderation is something I like to tinker with, and my own experiments have increasingly lead me away from karma. But there is no doubt that it is one of the most effective forms of soft moderation we have today, though I see little reason to believe that it can effectively scale past tens of thousands of users.