You already had this problem pre-UTF-8 in Windows: changing your default codepage could cause app fuckiness. So giving the user the option to use UTF-8 is reas

You already had this problem pre-UTF-8 in Windows: changing your default codepage could cause app fuckiness. So giving the user the option to use UTF-8 is reasonable. Making it the default is also reasonable given the problems that the Best-Fit mapping are causing, though Microsoft would have to do something to help users easily figure out how to run older code. Another not-so-reasonable thing would be to drop all mappings to "special" ASCII characters from the Best-Fit mappings, though this wouldn't help apps linked statically with the CRT. Not so reasonable because it doesn't fix the vulnerabilities. Sometimes security vulnerabilities motivate backwards-compatibility breakage.