Locales should have died long ago. You use plain data, stop parsing it depdending on wen your live. Plan9/9front uses where right long ago. Just use Unicode everywhere, use context-free units for money.
Locales are fine for display, but yes they should not affect what goes into files for transfer. There have always been appropriate control characters in the common character sets, in ASCII and most 8-bit codepages there are non-printing control characters that have suitable meanings to be used in place of commas and EOL so they could be used unescaped in data fields. Numbers could be plain, perhaps with the dot still as a standard decimal point or we could store non-integers as a pair of ints (value and scale), dates in an unambiguous format (something like one of the options from ISO8601), etc.
Unfortunately people like CSV to be at least part way human-readable, which means readable delimiters, end-or-record markers being EOLs that a text editor would understand, and the decimal/thousand/currency symbols & date formatting that they are used to.
Locales are fine for display, but yes they should not affect what goes into files for transfer. There have always been appropriate control characters in the common character sets, in ASCII and most 8-bit codepages there are non-printing control characters that have suitable meanings to be used in place of commas and EOL so they could be used unescaped in data fields. Numbers could be plain, perhaps with the dot still as a standard decimal point or we could store non-integers as a pair of ints (value and scale), dates in an unambiguous format (something like one of the options from ISO8601), etc.
Unfortunately people like CSV to be at least part way human-readable, which means readable delimiters, end-or-record markers being EOLs that a text editor would understand, and the decimal/thousand/currency symbols & date formatting that they are used to.