Forget commenting on anything that won't hit the front page.
Also forget commenting later on in a story when it gets stale. Best to hit a hot story when it is fresh and a lot of other people will be piling on later.
I'm amazed that you would have a karma system, special colored status indicators, and yet people would still claim that it doesn't affect user behavior.
That's the point, guys. If the karma/colored system didn't affect user behavior, it wouldn't be there
Create a game, and people will play it as a game. Put a number next to someone or a color and people will change behavior to change the color/number. Especially hacker/gamer/competitive males, which are clearly represented pretty well here at HN.
Forget commenting on anything that won't hit the front page.
Also forget commenting later on in a story when it gets stale. Best to hit a hot story when it is fresh and a lot of other people will be piling on later.