In its 81 year history, Marvel comics has made more than few creative blunders. They have allowed prominent creators a level of control that would ultimately prove detrimental to the characters they had been entrusted with. In other instances they have relied upon shock value to increase sales and draw readers back to a flagging title, usually by "killing" a significant character, bringing another back from the dead or replacing the face behind the mask.
Regardless of fan reaction to a given creative choice, the on-going narrative of superhero comics will mean that such choices will need to be undone. In these instances, the publisher is left with no choice but to "retcon" the situation. This is basically an industry term for an often clumsy "Deus-Ex Machina" that resets the pieces on the board and allows new stories to be written from a relatively common baseline.
In some cases though, if the change is small enough or niche enough then Marvel go with the other tried and tested formula of "sweeping it under the rug" and acting as if it didn't happen. Which leads to fascinating oddities that manage to be both in and out of continuity.
It is some of these "Schrodinger's Plot-Threads" that need to be talked about now...