I think it took me to get to 50 before I could downvote, although it's possible I've misremembered.

But that's not what he asked.

But pointing out these effects shows that certain "rewards" are provided for achieving certain levels of karma. Isn't it reasonable to guess that providing rewards was instituted at HN with the hope to encourage people to think about karma? [ and even more so the reward of improving an application to YCombinator, as an above link suggested? ]

pretty sure it was till he edited the question