I'm just tired of the signal pollution, and would like to be able to use karma to honestly appraise the worth of my articles and posts, without seeing 80% of my downvotes come in chunks that correspond precisely to how many posts I've made since the last massive downvote spree.
EDIT to add data points:
Spurious downvoting stopped soon after I named a particular individual (not ALL downvoting stopped, but the downvotes I got all seemed on-the-level.)
One block of potentially spurious downvoting occurred approximately one week ago, but then karma patterns returned to expected levels. I consider this block dubious, because it reasonably matches what I'd expect to see if someone noticed several of my posts together and disagreed with all of them, and did not match the usual pattern of starting with the earliest or latest post that I had made and downvoting everything (it downvoted all posts in a few threads, but not in other threads), so I'm just adding for completeness.
Spurious, indiscriminate downvoting started up again approximately half an hour ago on Sunday (12/1/2013), around noon MDT.
Edit: And now on Tuesday, 12/3/2013, at 10 AM, I'm watching my karma go down again... about 30 points so far.
Edit: And now on Saturday, 12/14/2013, at 2 PM, I'm watching my karma go down again... about 15 points so far, at a rate of about 1-2 points per second.
If it's bad, it's bad, and you might not know it. Why not ignore feedback in general?
Karma might be a relatively unreliable proxy, but it certainly isn't just noise.
The question is, what is karma an unreliable proxy for. Is it "quality"? Why would the output of a karma system even correlate with this -- it's a "vote" among a fairly heterogeneous (with respect to any given topic) audience. It doesn't really correlate with quality on slashdot, for example. My theory is karma is the measure of how well the post plays among various LW social coalitions.
It seems my problem with karma is the same as my problem with Wikipedia. You do want feedback, but you want feedback from experts.