There have been some arguments regarding the rules of time travel within the Marvel Universe, and whether One More Day violated those principles. In some stories it had been suggested that any instance of time travel creates a parallel universe.
But in the Fantastic Four, Reed Richards explained that the Universe sometimes corrects itself. If it’s not Marvel’s official explanation, it should sufficiently muddy the waters so that a reader is unable to definitively state that time manipulation doesn’t work the way it was presented in OMD.
There is no ONE official position for time travel.
Though some characters HAVE stated certain rules, we have seen time and again in comics from the FIRST Marvel time travel stories in the 60’s up to present day where they do NOT adhere fast to ANY one rule.
The rules of Marvel time travel have even been broken IN stories where those rules have been clearly stated– when you bother to take the time to work out those stories’ own internal logic.
In response to the suggestion that time travel in fiction needs more explanations than OMD/ OMIT provided, he countered…
I’m sorry that something as wondrous as magic can’t be a component of time travel in your view of fiction– despite the number of times it HAS been used in the Marvel Universe… and going all the way back to one of the greatest time travel stories of all time, Charles Dickens’ A CHRISTMAS CAROL where ghosts were the instruments of moving through time.
The Marvel Universe is a tapestry woven by many hands. Different writers will find comfort in some pre-established rules, others will find interesting wrinkles in other pre-established rules, and still others will want to travel down different paths and establish rules of their own.
Some argue that Marvel’s trying to have it both ways, trying to suggest that the marriage was significant enough to limit the writers, but not significant enough to have actually affected previous stories. in a substantial way. This goes back to Quesada’s point that for the most part, any story you could do with a married Spider-Man could be told just as easily with an unmarried Spider-Man, while the same is not true of any story you could do with an unmarried Spider-Man. So, the absence of the marriage made a difference in One Moment in Time in a way that it would not have made a difference in any preceding story. And the rules presented in OMD also helped.
Since Mephisto explicitly said that he was manipulating things to remove the marriage while keeping almost everything else intact, there’s an official explanation for why the changes were so minimal. This doesn’t confirm that the marriage was unimportant, since it does suggest that it was difficult for Mephisto to change the universe to fit the requirements of the deal.
The “For want of a nail” verse is often mentioned in any arguments about this, but it suggests a misunderstanding regarding causality. While an individual nail has the potential to make a difference, it doesn’t always happen. Hell, it usually doesn’t happen. Thanks to What If?, readers have been conditioned to think otherwise. But the only reason What If? type series feature significant differences is that readers aren’t going to pay to see a story about a minor change. Though it would be kinda funny to have a What If? one-shot that reprints an earlier issue by giving Peter Parker a different shirt for one page.
There are some semantics questions about whether time travel actually occurred in OMD/ OMIT, or whether it was something else entirely, such as a delivery from an alternate world. There were some suggestions that whatever was sent back in time would no longer exist once that timeline was altered, although sci-fi stories have conditioned us to discount that particular paradox. In the Marvel Universe, we’ve had storylines in which characters have have had consequential encounters with individuals or objects from possible futures. When those futures no longer exist, the ramifications on the present still remain.
The queries do tie into another topic of examination: Did Marvel succeed at defining what happened in One More Day?