Hmmm. It's true that one of the cases where I'm most likely to upvote is where I see a comment that looks fine to me that has a negative point total. But flash downvoting won't necessarily produce any negative point totals, and I'm a lot less likely to spring into action for a post that merely doesn't have quite as many positive points as it should (since I rarely have a very firm idea of how many positive points anything should have). Then again, perhaps in cases where nothing actually goes negative, not much harm is really being done anyway. So I may agree with you, but I'm not sure you've got exactly the right reason.

I guess mostly my own feeling is that the karma system seems to work pretty well as is. When I see a comment getting downvoted to oblivion, it usually seems to deserve it, and the quality of conversation around here usually seems above the internet average. I'm sure karma doesn't precisely measure what it's supposed to measure (whatever that is anyway), but I'm inclined to suspect that trying to make it do so is likely to end up being more trouble than it's worth.