Working with UTF-8 in the kernel

Working with UTF-8 in the kernel

Hopefully the filesystem records what mapping it was created with, like NTFS does. Otherwise, some of your files may become inaccessible when a new mapping is switched to (which, iirc, did happen on HFS+ before. That's not good...)

This seems like the key to me. If the case folding rules can change, there's no way to guarantee that the same file will always be accessible the same way, and that's true whether the case folding happens in the kernel or in userspace.