Aaron Griffin I am almost certain we are talking about “no to intended outcomes when no move has triggered”. If a move is triggered, the move “decides” the outcome or at least provides the script for the decision.

But in the absence of a move, sure, I say no in one way or another to people all the time in PbtA games as GM, depending on circumstances and how hard a move it seems is called for. Its actually been the hardest thing for me to learn to do, because years of other games had taught me to say yes.