I'm aware that's the correct pronunciation (I read a review of an action figure of him, years ago, where the author complained about that too), but, I've always pronounced it Constan-teen, and, even when I mentally remind myself that it's supposed to be Constan-tyne, I can't shake the habit. I don't recall him correcting people about it in the comics, as it's probably been at least a decade since I've read any of them, but, I'll take your word for it. It might be one of those things where multiple pronunciations are accepted too? I also tend to think more of the feminine form of the name, Constance, because one of my co-workers is named that, as was her elderly Aunt, whom she was named after, and recently passed away (but, of course, they both went by Connie instead).