Joe Quesada doesn’t want characters to smoke in any Marvel comics because he feels it delivers a bad message to children. He also shot down the idea of Peter Parker being the father of Gwen Stacy’s twins in J. Michael Straczynski’s poorly received “Sins Past” storyline in Amazing Spider-Man because he didn’t like the idea that Spidey had had unprotected, premarital sex. He also insists that simply divorcing Peter and MJ would irrevocably taint the characters and once again send a bad message to children. But trading off your immortal soul in exchange for a favor from the Prince of Darkness? Have at the one kids!
Now, I don’t believe in the devil. I know you can’t realistically do that in the way you could do the other three things I mentioned. I also know Mephisto isn’t really Satan, but in the Marvel U he might as well be. But I also know that there are people do believe the devil is real. And if you’re the kind of person to consider all these things to be real possibilities and really bad things, which one do you think would be the worst?
And the fact that Spider-Man trusts Mephisto and accepts the deal? Hasn’t he seen or read any of the hundreds of stories where the devil promises someone something fantastic only to somehow screw them over? Spidey’s supposed to be smarter than that.