I've been meaning to talk about that post. While I don't agree with John that it's a peripheral move, I think the MC should treat it as such.
As Mike knows, my group uses the hell out of Seize and it SHOULD be a Seize most of the time.
As a MC, I've learned to let them do that to each other, but I never put the PCs in a spot where Seizing is a move that makes sense with NPCs. I don't force them into a situation where my setup move has that much of a drop on them.
After watching a lot of television with AW moves in mind, Seize by Force situations DON'T happen in better fiction. Go Aggros, Manipulations, Acting Under Fire and it's consequences, all of these end up telling better, more dramatic stories than a Michael Bay Seize by Force.
In the past, I've hit the PCs with random violence, but I've learned that the threat of potential violence and consequences make for a better game and more interesting situations.
But more on topic, Act Under Fire is the most basic move. A lot of the others are just more complicated versions. In other words, you're acting under fire and the fire is BessAnn's sultry looks or you're acting under fire and the fire is LoJack all up in your face with a bigass gun! But these are Manipulate and Go Aggro, of course.
So there's no real need to offer the other PC a chance to react because their reaction is built into the move.
That said, since the moves are scalable (in that you can Go Aggro on Barry with a gun or you can Go Aggro on a town with your gang), sometimes the PC would have a chance to react, if it makes sense.