Flip Flop of God: After a number of "He's just sleeping" theories popped up amongst the fandom in regards to the Protagonist's fate, The Answer unequivocally states that the Protagonist isn't sleeping, he really is dead; only for Persona 4: Arena to state that he is, in fact, sleeping & not actually dead.
God Never Said That: Some fans spread the notions that Evokers were given the shape of guns in order to entice Akihiko (false: the Evokers existed long before Mitsuru even approached him) and that they "shoot Nyx's feathers" (false: Nyx Avatar didn't even exist when the Kirijo Lab accident happened, and Evokers have always been meant to simulate real guns.)
That said, Evokers do each contain a Plume of Dusk, but rather than shooting it, it helps assist in the summoning. Nyx has also been around for a long time. See more here, here, and here. Note none of this so far has been retconned, as the Kirijo group's study of the Plume of Dusk is the basis for Labrys's story.