Don't know about other UNIXes, but at least on GNU/Linux, neither IMEs nor filesystems are working with text data - it's all binary strings (with a few restrictions, like unacceptability of NULs). The only place where those binary strings are converted to text is when they're rendered (and this may cause some encoding-related oddities). So, sure one can do that.

I would've actually preferred for identifiers to be Unicode text strings.