The thing is, fonts are copyrightable but typefaces aren’t. Typefaces are the symbols, fonts are the files that contain all the symbols along with the formatting and everything else that let you use the typefaces in software. So he probably can’t copyright the symbol itself and it’s doubtful he could get a trademark on it either. But at the same time, copyright is also weird in that if he made an image and had that X in it, he would have the copyright to that specific image. But that’s only insomuch as anyone else would also own the copyright of an image they made with the stupid X in it.