In AW's text Vincent never says: "Every time the MC opens their mouth, a move has to come out." or "If you don't make a move right now, I swear I'll come to your table with a hatchett."
As you said, MC moves seem to merely serve as pointers and reminders to say what Vincent suggests are "more things, a wider variety of things" to say. But I would say that more than that, they provoke you to say one of those things.
I don't think there's more to that with regards to any possible other "mechanical functions" that they might serve with regards to the conversation. They are, essentially, quite a simple and straightforward mechanic.
Where complexity, depth, and importance arise, I think, is when you consider the power that such a tool gives you when it comes to pursuing your agendas without the need to think too hard about whether or not you should be doing that or something else instead. Suddenly you have a very simple and straightforward answer to the question "How do I contribute meaningfully to the fiction when it's my turn while pursuing my agendas and principles?"
In the last couple of months, I've seen a trend in 5e forum threads of people engaging in conversation about how often we downplay the high cognitive load that running a game entails. I think MC Moves are a tool that comes to our rescue in this regard. They free up space for us to think, to wonder about other aspects of the game...more room for the MC to play to find out.
I think over the years people thought of MC moves and said: "Sure...but this isn't too different from what I've been doing all along". I think they were missing part of the point of the mechanic. Right, they were already saying a wide variety of things that included some of those things, some of the time...but was it as clean and straightforward as MC moves provoke them saying those things? Did they have the confidence that, as long as they were aiming at an agenda and were misdirecting, barfing forth, being a fan, they would be fine?
Apocalypse World is very actively deceptive about most of its stuff. It is, in a way, a reaction to other "narrativist" systems where an in-orderly amount of focus was placed on meta-situational discussions and concerns of interesting situation, conflict, kickers, bangs, escalation etc... MC moves are a way for the MC to play instead of manage the game. I think that's powerful.
Okay, that makes sense.
This seems to imply that it's fairly easy to make a bad/unsuccessful PbtA(ish) game (one in which the circles come apart as per the diagrams on
the anyway page that you linked to).
I'll try and explain this implication that I'm seeing.
First, consider this example from the "Moves Snowball" example of play, on pp 155-7 of the 1st ed rulebook:
I’m still making my hard move. . . .
". . . 4-harm area messy, a grenade. You have armor?”
“1-armor.”
“Oh yes, your armored corset. Good! You take 3-harm.” She marks it on her character sheet. “Make the harm move. Roll+3.”
She hits the roll with a 9. I get to choose from the move’s 7–9 list, and I decide that she loses her footing.
“For a minute you can’t tell what’s wrong, and you have this sensation, it seems absurd now but I guess it makes sense, that you hit the ceiling. Maybe you tripped on something and fell, and hit it that way? Then gradually you get your senses back, and that noise you thought was your skull cracking is actually your door splitting and splintering down, and that noise you thought was your blood is their chainsaw. What do you do?”
“I set off my pain-wave projector.”
“Sweet,” I say. “That’s…”
“1-harm area loud ap.”
“The loud is their screaming,” I say. “They’re like -” and I hold my hands over my ears. On a whim, looking through crosshairs, I add, “Church Head isn’t. He looks paralyzed, he’s rigid and silent, his eyes are rolling around in their sockets but otherwise he’s not moving.” Taking 1-harm is much worse for NPCs than it is for PCs; see pages 167–168. “What do you do?”
“I have my violation glove on,” she says. I don’t dispute: of course she does, she always does. “I pick my way over to Plover and put my hand on his cheek. I do in-brain puppet strings to him: protect me.” She rolls+weird, hits a 10+, and smiles sweetly and with malice.
A subtle thing just happened. I’ve been saying what they do and then asking Marie’s player what Marie does, but here she’s seized initiative from me. It isn’t mechanically significant, we’ll still both just keep making our moves in turn. It’s just worth noticing.
“Hot,” I say. “Whackoff grabs you from behind to pull you off of him, but Plover jumps on her.” (I hadn’t mentioned before that Whackoff’s a woman, but she has been all along in my head. Ha ha, gotcha.) “He’s punching her in the face, she’s falling back, she’s like, the f***? This uses up your hold over Plover, right?”
“Right,” Marie’s player says. “That’s okay. I pick up his chainsaw and chop into them both.”
Damn. I’m impressed.
“That’ll be seizing something by force. Their, um, meat. Roll it,” I say.
I have absolutely no interest in saving these NPCs, none. I’m looking at them through crosshairs, and much as I like them, I do not make them safe.
Baker refers to the MC and Marie's player "making our moves in turn". Unpacking those moves:
* The MC inflicts harm - a hard move, as Baker notes.
* This triggers the harm move, which the player rolls.
* The MC has Marie lose her footing, which puts her in a spot - a soft move, as nothing irrevocable results from it. It changes the fictional positioning, but doesn't step up the intensity of the conflict.
* Marie's player declares that Marie activates her pain-wave projector, which is not a move as such.
* The MC describes the effect of the pain waves on the NPCs - Baker doesn't call this out as a move, but to me it looks like another soft move, offering an opportunity to Marie's player at a cost to Keeler's player. To me, this does seem to step up the intensity/stakes of the conflict, by tempting Marie's player to go all out. (And we see this pay off on p 158 - "Keeler’s player is scowling and shaking her head - they were both members of her gang.")
* Marie's player triggers in-brain puppet strings, and rolls for it.
* The MC describes Plover defending Marie from Whackoff - what move is this? Again, Baker doesn't tell us. I think it's taking away Marie's stuff, namely her hold over Plover.
* Marie's player goes at them with the chainsaw, triggering seize by force.
I think the absence of action economy here, in the classic RPG combat/wargame sense, is probably counterintuitive to a lot of RPGers. What holds the play together? The prompts to the GM/MC that arise out of the player-declared actions (activating the pain-wave projector, in-brain puppet strings, seizing by force) and the invitations to action issued by the GM-side moves (putting Marie in a spot, offering Marie the opportunity to take on the gang members, taking away her hold over Plover by having Plover and Whackoff fight). I don't think it's trivial to achieve this in RPG design.
Pages 283 and 284 of the rulebook diagram out various moves, and show how they manage this interplay of prompts, invitations etc.
Get any of this stuff wrong and you'll have a weaker game - one where the circles come apart. My go-to example for this comes from Classic Traveller: the move is
if you drive your vehicle for a day, then throw to see if it suffers some sort of failure. But how do we know if you've driven your vehicle for a day? That never comes out of the conversation: some other process that the rulebook doesn't guide us on (eg map-and-key resolution) is needed.
I think someone who says that GM/MC moves just list things they've been doing all along may not be having regard to all these
other things they've had to do to make their RPGing work.
I just don't think that Apocalypse World in any way, shape or form, expects you or encourages you, the MC, to manage all of these concerns about framing, and conflict-neutralness and GM fiat...specially not while you're playing. It frees you from that with the tools it gives you! It tells you, straight to your face: when it's your turn to say something, you know, pick one of these.
(Small parentheses: One tool to make sure there is no conflict-neutralness in your Apocalypse World is threat creation in between sessions. A small bit of management to make sure you can get back to playing with fresh new things to say next session.)
That answers the OP's question about the role of fronts/threats!
I think the example of play also helps answer the question about
when to roll the harm move. In the example it helps develop the fictional positioning, creating the prelude to Marie activating her pain-wave projector. If the fictional positioning is already developed enough that players are declaring actions in response, then maybe the harm move isn't really needed on that occasion.