We may want to take that report with a grain of salt for Scheme. A
simpler approach would be to define Scheme identifiers as everything
_excluding_ the reserved punctuation characters, optionally allowing
Unicode variations on those characters and extending the definition of
whitespace. Most Schemes already work in this manner, despite the fact
that R5RS uses an inclusive list. With a quick check, the *only* Scheme
I found that doesn't let me enter and use arbitrary high-bit UTF-8
identifier names is Kawa, regardless of the Scheme's internal encoding.