Joe Franklin wrote:
"To me, it would be comparable to someone trying to spell my name 'Jo' instead of 'Joe' (it happens a lot). A simple correction usually works. Not sure why some folks insist that it's okay to spell something wrong, decrying it as no big deal, or as their 'right'."

Precisely. I mean if someone has only ever heard a name and never seen it written. This could be true as regards superheroes if the "fan" in question isn't a native English speaker and has therefore only ever encountered the name as given in his own country, eg. Spider-Man used to be "Spindelmannen" in Sweden though I believe he's called Spider-Man these days. But as soon as said person has seen it written, as soon as said mistake has been pointed out, there's no longer any room for defending the misspelling.
Arguably, it would be less offensive to use a correctly spelled Spidey, which is after all a nickname used by creator and character alike in many of these stories, than using a misspelled Spiderman instead of a correctly spelled Spider-Man. At least the nickname, while a nickname, is spelled correctlky and as such given due courtesies and respect, the misspelling is just a misspelling whichever way you look at it.

JB wrote:
"I have been mocked for 'pronouncing' the apostrophes in J'Onn J'Onzz. Juh-on Juh-owns.
I wonder how those people pronounce names like O'Brien or O'Hara?"

While I agree with your pronunciation of J'Onn J'Onzz, JB, I doubt these people would have such a hard time pronouncing O'Brien or O'Hara as apostrophes are more easily understood by most people if they follow a vowel rather than a consonant. I think it's the consonant + apostrophe that causes these people problems and then they are unable to deal with their own inability to pronounce it, so they pick on other people.