Does Standard ML support Unicode?
I believe it does not but cannot find any authoritative documentation for SML stating such.
A yes or no is all that is needed, but you must know for a fact. No guessing or I believe answers. An authoritative link would be better.
Not really. All there is in the standard for the time being is the ability to use \uXXXX escapes in character and string literals, and that it does at least allow Unicode as the underlying character encoding for char or the optional WideChar.char. But the standard basis library does not prescribe any support for additional Unicode-aware functionality.
Particular implementations may have additional support, and you may perhaps find some third-party unicode libraries, but that's about it (unfortunately, I have no pointers at hand).