CHR$128 doesn't work entirely
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thunor
Panic HR (panicohr.p) is a good example of this. Some characters have been redefined but not all, so this requires looking into. I don't actually know anything about this "scheme" but I can always look through the panicohr.p code and see what it's doing.
There are plenty of CHR$128 example programs on http://zx81.eu5.org/toddysofte.html