Just never ever use either , or . as a thousands separator and there is no problem. Even if you ignore the international aspect, both symbols look too much alike and can be mistaken ("100,000.00" and "100.000,00" visually suck even if both are technically well defined in some countries).
Use spaces instead - both "100 000.00" and "100 000,00" are unambigious to anyone, regardless of language background.