People are aware of it -- Unicode has casefolding rules which apply to all Unicode characters and are supposed to solve this problem, but I believe you can run

People are aware of it -- Unicode has casefolding rules which apply to all Unicode characters and are supposed to solve this problem, but I believe you can run into issues when the casefolding rules end up not using language-specific characters (meaning that any language information is lost in the translation). Another example of this is the German eszett ("ß".upper() == "SS" but "SS".lower() == "ss" != "ß").