Sort of. Consistently making smart comments carries a lot of weight in getting an invitation to YC interviews. It was the deciding factor for at least 3 people we funded: danielha, alexwg, and one other I probably can't disclose because they're not launched yet.
It's not simply a function of karma, though, but whether we recognize the username as someone who seems smart.
Only if you think the "game" is to accumulate karma. For me, the submissions are merely seeds around which insightful discussions grow.