It doesn't seem at all sensible to me that the principle of "acting as one would formerly have liked to have precommitted to acting" should have unbounded utility.

Mostly agreed, though I'd quibble that it does have unbounded utility, but that I probably don't have unbounded capability to enact the strategy. If I were capable of (cheaply) compelling my future self to murder in situations where it would be a general advantage to precommit, I would.