Earlier quoted context omitted.
You could take the log of any score > 1 to reduce the incentive to game the system.. that way someone who relentlessly karma whores won't have that much more influence than a mildly uprated commenter, but both will have more influence than a noob.
but then a mob of noobs could outrank two wise elders.
Well, with the situation we're in now, only three noobs (or one noob with three accounts) can outrank two wise elders. As to your gp comment, yes, incentivizing karma gains could be a problem, but that's the tradeoff that's got to be considered.
I'm not sure what the best tradeoff is; personally, I'd probably go with something like Pagerank for a while and see if the comment quality (above the fold, at least) improves, but perhaps pg has a desire to keep things more neutral and fair, I'm not sure.