Using comma would probably caused more problems as it is a decimal separator for those languages. My excel also uses semicolon in formulas instead of comma when separating parameters. Some VBA scripts break when using different language settings and some forumilas don’t translate automatically to different locale so they just give an error. Overall using excel in different locale setups is annoying.

Best separator I have used is | as i have never seen it in the data as an input. Comma and semicolon both have caused issues in the past for me as they might pop up at wrong places.