Unicode case folding is a complicated algorithm, and its definition is subject to change with updated Unicode versions. It's nice not to have to worry about that.
Okay, but I don't think this has anything to do with the use case JohnFen mentioned or my questions about it.
If your goal is super easy filename generation then you're probably not going to leave ASCII.
And if you do go beyond ASCII for filename packing/generating, then you should instead use many thousands of CJK characters that don't have any concept of case at all. Bypass the question of case sensitivity entirely.
