>This is because for any given task there are a million ways to get things wrong, but only one/very few ways to get things right. So people learn almost nothing from "don't". You can eliminate negative feedback altogether and lose almost nothing.

I would say, rather, that any "don't" should be paired with an "instead, do X when attempting to do <thing they were trying to accomplish>". "Don't do this one narrow thing" does very little to shrink their search space, while a concrete alternative does a lot, and is actionable.

(And yes, I've followed my own advice by saying "don't say 'don't', do it this other way instead"!)