Here is an idea. Individual karma scores, no matter how they are scored, will create certain kinds of incentives. What if you create a global karma score for th

Here is an idea. Individual karma scores, no matter how they are scored, will create certain kinds of incentives. What if you create a global karma score for the entire site, which is an aggregate of all user activity? Posting, commenting, voting, would all not only be scored for each user individually, but for the site overall, or perhaps in the future topic categories could either be teased out by hand, or assigned using some NLP technique like LDA, and each topic could have a score. It would at least be interesting to see the health of hacker news on a 0-1 scale somewhere on the top menu bar, and maybe some little stats behind the score to help illustrate the thought process behind the score. You could use cosine distance for each posting from the n highest scoring posts, and take the inverse of the sum of the distances to score a potential for each post. The sum of all the potentials of all postings within a certain time period, taken as a ratio over a trailing average potential over a longer period would a an interesting way to possibly get a view into how diverse and how high quality each posting tends to be. A sitewide score would also allow you to make each user's score be a weighted combination of individual score and their contribution to the whole. Consider it a form of shared fitness.