I'm concerned about this move of the Wizard:
Know-It-All
When another player’s character comes to you for advice and you tell them what you think is best, they get +1 forward when following your advice and you mark experience if they do.
What keeps every player from constantly asking questions like, "I am under attack. Shall I defy danger?"? It seems like all PCs in a party with a Wizard would always have +1 forward, and in no time they would have a level 10 Wizard in the party.
Let's have another look at the Know-It-All move (emphasis mine).
Know-It-All
When another player’s character comes to you for advice and you tell them what you think is best, they get +1 forward when following your advice and you mark experience if they do.
Now let's look at your proposed scenario: the Fighter is under attack and you've asked him the all-important question "What do you do?". In this scenario there are plenty of barriers to the Fighter getting his +1 forward and the Wizard gaining his experience. They could be overcome if the fiction allows it but would take some doing.
All in all, what you should remember is that Dungeon World is always Fiction-First. Your players don't tell you what moves they're using, they tell you what their characters are doing. If their fictional actions trigger a move then you as the GM let them know that they're about to trigger a move and ask if that's what they want to do.
Moves represent game-mechanical actions tied to fictional cues. When another PC "comes to [the wizard] for advice," that's likely to be, like, a little scene. This move is clearly about the wizard being the educated expert (likely annoyingly overeducated, hence the name).
In Dungeon World, the GM decides when a move is triggered. What's going on in the fiction? Does it make sense that the wizard could, like, give helpful advice here? You don't want to pigeonhole the players out of spite or whatever — it's a flexible, free-wheeling, collaborative game. But if you (as a player or GM) think someone just trying to screw with the rules instead of following the spirit of the game, you should employ this tried-and-true fun-saving technique:
tilt your head, cock your eyebrow, and intone the magic word: "Really?"
That's not what the move says. A move applies when it's fictional description happens, and there is a significant difference between “[a] character comes to you for advice” and “[a] player […] asks [you] questions”. So, if the other players just ask you any random question at the table, this move does not trigger, and no imbalance is done.
However, if another character is actually under attack, turns to the wizard (who might be busy with her part of the fight), interrupts her and asks her what to do, this move could possibley trigger, and all the other implications of the fiction would have to trigger as well, in particular that the wizard now pays attention to the other character's foes and not her own situation (how else is she going to give advice), the advice seeker could be directing attention of his foes to the wizard, etc.
(Obviously, “Coming to someone for advice” in the real world normally imply “having a conversation”, “being in a somewhat private environment”, “spending some time thinking about the alternatives”, “expecting the advisor to have relevant knowledge” etc., so it might not actually trigger, depending on your table. But even with minimal assumptions, which allow triggering the move in the middle of a fight, doing so would definitely constitute a Golden Opportunity for the GM, which should remove your concerns about this move.)
In general, the clear implication of this move is that the wizard has a large amount of experience and/or knowledge, and is therefore qualified to give helpful (thus the +1 forward) advice in any (Note how the move is called Know-it-all and does not contain a restriction such as “for advice about …”) situation.
Most answers here focus on the possibility of the characters engaging in useful dialogue that could trigger the move in a combat setting. I'd like to offer another approach:
Remember that the wizard is a know-it-all in the literal sense of the phrase. What they say is probably a useful fact. It's not just for a one-off +1, it is truth in your fiction.
So if someone, regardless of circumstances, manages to get the wizard's advice, do ask the wizard for the details, and make that answer part of your world. (Ask questions and use the answers) Think of how that little factoid affects things, and use it whenever it presents an interesting vector for you to follow as the GM.
And if the circumstances make it hard to launch a fruitful Q&A session with the wizard, resolve that with the usual approach for harder situations, and if the players managed to navigate it, then they have earned it.
— I ask Wizzrobe how I can hurt this critter.
— Oh, as I said a moment ago, it is bringing down its claws on you, how do you intend to ask a question while being sliced?
— Hmm, I crouch and hide behind my long shield until I get an answer…
— Great. That looks like defying danger by powering through, so please roll+STR
— Ok. What does an 8 give me?
— Well, while you were holding a pleasant conversation, your shield bent and buckled under the incessant claw-pounding, sacrificing itself to protect you. I don't think it would be useful for any more. By the way, what was the question again?
— How to hurt this clawy critter…
— Wizzrobe, you tell us.
W: These things have very sensitive ears. Hit it in the ears. That would hurt it a lot.
— That's exactly what I do, I use my backup dagger to stab it right in the ear. Hack&Slash baby, 11 for the roll with the bonus and 6 for my damage roll!
— Yes the critter screams with agony as you put the dagger in its ear. It's not dead yet but takes a step back and will probably avoid confronting you if possible. But a few seconds later, you hear similar scream-howl like sounds from the surrounding mountainscape. Are they echoes or responses, you can't tell. What do you do?
As a GM i just wouldn't let them abuse mechanics like that. After all something like that wouldn't be very DungeonWorld-esque...
On the other hand I might let them play it out and, eventually the wizard might be so distracted by the constant questioning that he fails to recognise the random Goblin sneaking up on him.
