Filesystems and case-insensitivity

If I understand you correctly, I agree. Adding filename-as-natural-language-text semantics rounds off one of the many sharp edges in shell scripting. Adding bumpers around the rest is a separate task.

If the semantics really are to be changed – if a differentiable set of path elements are to contain text and only text – that's a useful feature from an application developer's perspective. If it's to be a new kind of hard-to-predict weirdness, that's less useful.

I'd prefer it if text-only filenames were limited to printable graphemes only. That might be too high a bar. I would hope that control characters (C0,C1) would be disallowed. I don't consider \x7F (DELETE) or \x09 (TAB) to be valid in a natural-language name.