Disclaimer: This is an answer to the previous post. I will take a look at the new one later on, sorry. Gotta run.
Well, when does the deceiver have access to the aspect? Immediately as soon as he 'creates' it or only when the duped party tries to invoke it? At what point does the duped realize he's been duped, if at all?
My understanding is that the deceiver does not "have access" to the fake aspect. He can't do anything with it unless the deceived tries to invoke it. Then he can either have the deceived waste the fate point (which disappears) or give it back and basically replace the fake aspect with a temporary one he actually
has access to (since he can invoke it). The deceived realizes he's been duped whenever he tries to take advantage of the aspect. I can't think of any other way at the moment, at least without delving into metagaming (which I dislike).
There's the argument that this leaves a person with a huge penalty. Example: If I think I'm going to be able to tag something for a +2 then learn I'm actually suffering a -2... Like in the event where the deceiver attacks, and I choose to use the false aspect to defend. At that point you learn the aspect is false and, instead, the deceiver tags that aspect for an additional +2. You're effectively 4 shifts lower than where you thought you'd be on your defense.
That sounds about right, with the addendum that I would think that the deceiver could
choose not to tag the aspect immediately (and to be nitpicky, it's the new temporary aspect instead of the fake aspect, but mechanically it's the same, in your example). Do you think it's too much? I think it fits, narratively speaking. It's basically a double-trap. The deceived thinks he has an advantage but it's actually what the deceiver wants him to think and is just waiting for the right moment to bank on it. It should be a big penalty.
Also,
if you choose to leave a free tag, what 'advantage' does the deceiver get? It's not like the guy is down a FP. What is the 'significant' thing you've learned from the deceiver?
I'm not 100% sure I get what you mean with the first question. Who leaves a free tag? As for what the deceived learns, "that aspect is fake and it was a trap" is pretty significant in my eyes.