The following is somewhat similar to the issue discussed at How to ask nicely in Dungeon World, but I'm not asking about someone "asking politely" for a concrete action or object.
I'm wondering how, by the rules-as-written, the GM is supposed to react to someone striking up a conversation with an NPC and it is not about wanting something directly from the NPC, or rather, they are just making friendly inquiries the NPC has no in-fiction reason to refuse to answer. (For a concrete example, in a dwarven settlement haunted by creatures from below they start asking one of the terrorized dwarves questions about how exactly these creatures manifest.)
As written, the rules seem to say that after the PCs ask the NPC a question, the GM has to make a move since the players look to them to see what happens. But there is no move like "give out information" – the closest is Reveal an Unwelcome Truth, but is the GM really supposed to come up with unwelcome truths as answers to every question a PC asks an NPC? The answer to the question linked in the beginning explicitly calls out that there is no "Have a freeform social interaction" move, but I feel something is lacking here. In some conversations, Reveal an Unwelcome Truth and Show Signs of Doom are perfectly appropriate, but none of the other moves seem to make any sort of in-fiction sense when the NPC is already established as a hapless peasant or a willingly cooperating scholar or some similar reliable source of information.
Think Offscreen could apply, but this leads to a very strange result where players "fast forward" the offscreen state of the world by asking many questions. I had a hilarious scene where the players tricked a ghost into possessing an egg and then Parleyed with it to henceforward answer their questions by shaking in the classic once-for-yes/twice-for-no pattern. But technically, every single one of these Yes/No questions should have triggered a GM move, since the players looked to the GM for the egg's answer after every question…and there were rather many of those. Making a GM move for every such question strikes me as patently absurd.
So, is the answer that sometimes, the GM doesn't have to make a move? This seems to run counter to everything else I've read about Dungeon World – the GM is bound by the rules as much as the players are, and "make a move when the players look to you to see what happens" is a binding, non-negotiable rule. Is the answer that if I play with a group whose style includes occasionally lengthy conversations without any stake or antagonism, I shouldn't play Dungeon World? I would be surprised at that because everything else about the session went so smoothly that I cannot fathom such an oversight in the basic design of the rules.
Best Answer
I think it's helpful to frame things in context of your Agenda: Portray a fantastic world, fill the characters' lives with adventure and play to find out what happens. What you do as a GM should ideally always be in pursuit of that agenda. Our goal isn't to simulate everyday situations and imagine "okay, how would your typical farmer respond to this question?" It's about embracing the fantastic and creating adventure. Always remember to think dangerous while remaining a fan of the characters.
If the PCs have time to strike up an idle conversation, they must be feeling relatively safe. Time to make a move. A few ideas (including a few you already mentioned):
Reveal an unwelcome truth: "It's good to see some adventurers in these parts. Folks have been feeling on edge ever since the Halvred Farm burned down" [most likely you're revealing a grim portent for one of your front dangers]
Show signs of an approaching threat: The man seems quite willing to strike up a conversation and you chat for a bit. Thief, you notice that a few men have stopped to watch your conversation and, maybe you're just being paranoid, but they seem like they might be moving to surround you... [This is in a context where the PCs are floundering a bit and trying to figure out what to do and the character they interacted with isn't very interesting; I choose to just shift the focus entirely]
Use up their resources: I don't know much, I'm sorry, but I am rather hungry. Could you spare a bit of food? [and if they say no, it's likely a chance for some character/bond development.]
Turn their move back on them: "Sure, I can help with that...(shares useful information)" [behind the scenes you note that the big bad learns about this conversation and knows the party is asking about him; ideally you foreshadow this a bit by portraying the NPC as a bit shifty or maybe highlight him briefly in a scene whispering to someone.]
Separate them: "I...have a sensitive question to ask of you; Cleric, can we speak privately?" [This can be a set up for a subsequent danger while the Cleric is occupied or might spur some character/bond development while the characters talk without the Cleric present.]
Give an opportunity that fits a class' abilities: "Bard, you do sense this woman knows something, but she seems hesitant to share the information" [basically an invitation to play with Charming and Open, which is a wonderful two-way move.]
Show a downside to their class, race or equipment: Fighter, she seems rather apprehensive of you. In fact, several of the people here are giving you that look. You hear a faintly muttered racial epithet for dwarves, though you're not sure who said it.
Offer an opportunity, with or without cost "Could you spare a few coin? I found something on my land that you might find interesting."
Put someone in a spot: Wizard, as he gets closer, you recognize the man as a friend from your childhood who you had a falling out with due to a betrayal. How did he betray you?
Tell them the requirements or consequences and ask: You can spend some time to press the man for information, but your quarry will get further away the longer you talk. Do you want to keep talking? [I'd usually also fast-forward through chit-chat at this point and jump to the key point.]