I'm considering stepping in to correct such injustices, but thus far my desire to vote up/down based solely on individual merit has prevented me. If it keeps up, let us know, and I'll start changing my strategy.

Don't. It probably happens to people who like the local Powers That Be, too. My karma dropped 17 points in 10 minutes some days ago, for no reason I was aware of. Karma doesn't matter all that much, and not acting like power-struggling children about karma does matter. Even if there is systematic injustice in some particular direction, there's better information-flow in pointing out the distortion and letting people consciously realize that karma is unreliable in such-and-such a way, than in adding further information-poor voting to try to compensate.