For those who already know how to play chess but want to get better (preferably quickly with minimal, targeted training), I wrote a guide called "How to Get Good at Chess, Fast" that hit #2 on HN: http://www.gautamnarula.com/how-to-get-good-at-chess-fast/
It's not really a rule, more like an observed behavioral pattern :)
The idea is that a comment should add something meaningful - constructive discussion, sharing your personal experience with the topic being discussed. Also, as far as I know, posts with high comments/votes ratio are penalized (flame wars detection).
Thank you for this, is there anything similar for getting better at math/problem solving? Right now I'm going through the art of problem solving series but I would like to incorporate more.