Perhaps the most important thing about upvotes and downvotes is how they affect visibility. Everyone wants their voice to be heard, and some people want the opportunity to influence whether other people's voices are heard or not, e.g. by flagging stories or killing comments through downvoting.
If the big deal here is visibility, then I would concentrate on the algorithms that decide when a comment thread is rendered gray or invisible and the algorithms that decide the ranking of comment threads. I would look for patterns of votes or commenting that might help distinguish "popular but fluffy" from "popular and thought-provoking."
This data is interesting because now if you randomly perturb the front page, say by putting a new story in position #5 and lying about how many points it has. Show this perturbed page to a small sample of users and see if the story beats the historical averages or not.
If that kind of thing worked, it could help correct for the phenomena where a popular story stays popular just because it's popular. You can now rank stories by how well they take advantage of their "real estate" on the front page. Those that underperform the average sink, those that outperform the average rise.
One hitch. This might not work if you tell people you're doing it.
I can't help but think in the case of RiderofGiraffes particular case karma might have kept him in the community longer than he should have, or burnt him out. Getting to the point where your contribution to a site is the auto-posting of popular content is probably a failure of the system.
In general karma serves as an incentive to contribute, but its a fairly shallow kind of contribution, and I don't this site needs that anymore. Hopefully comment and submission score without accumulation give enough encouragement to quality without encouraging quantity.