In this case simply buying out just doesn't seem appropriate to me. Do you think that was an appropriate buy-off? Convincing the troll that Maeve wants you to keep your staff is likely a social conflict in its own right. I would allow the player to accept the compel and then start such a social conflict (or try to sneak the staff in, or whatever), absolutely, I am not against players finding their own ways around obstacles. But in your second example buying off the compel is basically just making the compel "mystically go away."
Is the player
actually there to perform a service to Maeve? Then the troll leans his head in, gets the OK, and the player enters. Why slow the game down by making them come back out?
In any case, they are using their FP in exchange for the social skill roll to convince the troll. Remember how aspects created with skill rolls get a free tag? Skill rolls and FPs are somewhat interchangable. They use the FP to convince the troll. That's what they're really doing here. It's essentially the same as making the declaration "I convince the troll." You just
forced them to do it.
OK, lets look at that second example.
You show up out of the blue, the bouncer doesn't know you, Maeve may have heard of you, but isn't your friend. You say you want to perform a service and need to be armed. The troll probably says "You can have it back when you leave, you won't need weapons in there." He doesn't trust you, also he thinks your excuse is stupid. He knows that if you are performing sanctioned magic in the club you can easily come back with permission and pick up your staff, and if you are going in to get instructions and then leave to perform a service you can pick it up on the way out. The only reason he sees for you to want to be armed in the club is if you want it for protection against the fae in there.
Your deep and intricate reasoning and detailed character motivations here are nice to see. It shows how much thought you put into the world all on your own.
Have you explained this paragraph to your table? It's a very reasonable and rational explanation as to why he can't take it in. You could even escalate the compel with each couple sentences of that paragraph you lay out. "He doesn't trust you. Maeve hasn't told him you were coming. <slide a second fate point, escalating the compel> <Player buys off again> If you were going to perform sanctioned magic here, you could come back out and get it. <slide the third fate point, escalating again>"
Also, since we're talking in-character motivations, here, Is the troll really smart enough to think this entire, detailed motivation out? Trolls aren't exactly known for their sharp intellect.
Most importantly of all:As nice as your detailed thought process above was, it is also mostly irrelevant.
You need to talk with your table on this. If they don't think any encounter with the no-name bouncer is going to be an interesting improvement to the story and, more importantly,
they are willing to pay valuable narrative currency to avoid it, why are you trying to force them to play through it? Because you took the time to stat it out? That's nothing but hubris.
Just this weekend I ran a FATE game. I had planned out 3 different combat encounters. My players, through sheer cleverness, buy-outs and subterfuge, bypassed ever fighting a single one of them. And you know what? They
abosultely loved the session. Your players are telling you what they want. Why aren't you listening?