I ran across this in a reread of MMfM a few days ago. I don't have the exact phrasing of it in front of me, but it seems to be a reversal of normal karma where a choice is removed, and instead a choice is offered. As with normal karma, though, the gesture is repaid down the line in kind.
I'm still pondering the full implications of this, but so far it seems funny that doing something (profoundly) nice for another might not just be balancing a previous debt, but could also create an imbalance in and of itself. Any other thoughts on this kind of karma?