Sorry @TheGoldenKey maybe I’ve misread or misunderstood something in your opening post, but you wrote
Back in S1x19 The Return, Blue clearly tells Baelfire that what ails his father isn’t from this world (meaning Dark Curse isn’t from the EF).
Now I quoted, what the Blue Fairy said in that episode and she said definitely: It IS specific to the Enchanted Forest, to “our realm” to quote her again, and she and Bae were in the EF at that moment, or in less poetic words: The Dark One’s power IS from the Enchanted Forest. The vault is in the Enchanted Forest. Of course you can assume, the Blue Fairy is not from the Enchanted Forest and she was talking about “our” aka the Fairies’ realm, but I don’t assume that. So were is the Blue Fairy’s statement in contradiction of what we saw past episode?
She says furthermore, that “his powers don’t belong” in their realm. You read that differently, as the power doesn’t come from the Enchanted Forest, okay. As I read what the Blue Fairy said, the powers of the Dark One not only can come but do come from the Enchanted Forest (and can work in any land with magic). But the only way to get rid off them is by leaving and live in a land without magic (or to get killed and thus transfering the power to someone else, but the Blue Fairy doesn’t talk about that option).
My opinion: The Blue Fairy DIDN’T lie, NOR did the writers mess up at this point.
To me “not come from” or “is not from” and “not belong to” is not the same wording and has a very different meaning, and the latter is what is written in the script.
Can we agree on having a different point of view here?
edit to clarify