User blog comment:IamJakuhoRaikoben/Chapter 464: Natsu vs Zeref, Review./@comment-4933386-20151130223153/@comment-7418318-20151202203213

@FTF: It might be considered rude in some places to call your mother by first name, but in other places it's normal.

And remember that Alvarez is a different continent, so maybe this is one of the ways in which Mashima could try to make it feel like a difference place with different culture.