But this will not tell you if this multi-byte char IS or IS NOT a "letter" because it includes punctuation and other symbols.
Does anyone know how to know if it is a letter or something else?
Sure: Get the codepoint and test against all known "letter" codepoints
There must be a function somewhere which does it already,
IsAlpha() or something alike, but I don't remember where it is. Let me check ...
(
later) I haven't found (yet) anything as simple as a
IsUnicodeAlpha() function but there are some things it the
unicodedata unit (in {fpc-source}/rtl/objpas/unicodedata.pas) that may be useful to implement one.