I don't think many people actually care that much about karma. To care that much about karma yet still be willing to deliberately make mistakes that will be corrected seems like an unlikely combination. The positive good that comes from encouraging people to retract errors is likely a better thing than the tiny chance that some people will deliberately make such mistakes to gain more karma.
Regardless of whether people care enough to do this to get karma, I definitely don't care if others do it. It doesn't impact me if someone has sneakily gained 5, 10, or 100 points of karma.
An easy way to win cheep karma on LW: