I'm not OP but a related point is that locale-aware formatting can be offputting if your application is not actually translated into the language. At a previous

I'm not OP but a related point is that locale-aware formatting can be offputting if your application is not actually translated into the language. At a previous job we delivered an English-language product that used locale-aware number formatting. Our German customers asked us specifically to use English number formatting, both because it was a technical programming product and because the application was entirely in English. German number formatting with English text was undesirable to them, and they didn't expect us to translate into German. They saw it as an American product and that carried into their expectations about formatting. We went into the code and explicitly specified the American English locale for all string formatting, and they were happy.