"Martin v. Löwis" writes:
It occurs to me that the PEP maybe should say that it is an error to have your POSIX locale set to UTF-16 or something like that.
No. It is *impossible* to have UTF-16 as the locale character set, not an error. Your statement is like saying "it is an error to breathe in the vacuum".
I realize this is not useful, so maybe you don't need to mention it. However, it certainly is possible to set LANG with an absurd, or merely dangerous, encoding.
In any case, the discussion says
# Encodings that are not compatible with ASCII are not supported by # this specification; bytes in the ASCII range that fail to decode # will cause an exception. It is widely agreed that such encodings # should not be used as locale charsets.
Which is your excuse for not supporting Shift JIS fully. It doesn't stop people from setting LC_ALL=ja_JP.shift_jis, or using Shift JIS as the default encoding for certain media.