I'm in the same boat. I've noticed something interesting though. Back when I was commenting a lot more, I cared a lot more about my karma points. Now that I'm more of a lurker, I realize I don't keep track of my karma at all, nor do I really care about it anymore. So maybe actually, I don't care either way... but people like you and me do exist in terms of signal to comment volume ratio (at least, I hope my ratio's high :D).
Likewise with lurking-until-valuable. If karma were converted to an incentive for daily engagement, that would be a strong disincentive for me to even log in. It changes the relationship from a friendly "it's okay if you contribute, however often you feel like" to "be here and be loud, or be screwed".
(If I were changing HN, I'd love an option to replace the karma score with a reply inbox, so I don't have to poll my threads page. I'm trying to break myself of my post-and-run habits, of my general fear of defending my ideas, and of my overvaluation of karma.)
