I should perhaps clarify that "just use the win32 api" refers to on Windows. Just as one might use syscall 4/write() on Linux, if one doesn't want to/can use libc printf.
Note; I'm not convinced using utf8 internally is a great idea - especially for a "beginner friendly" language. Playing with anything from palindromes to revise strings and character/grapheme counts and
"d o u b l e s p a c i n g"
strings can be fun learning exercises - that might be easier with a 32-bit (or even 64 bit) representation.
But no matter how you look at it, there's no such thing as "simple" handling of international text.
I'm not sure how there can be "one true sane thing". There's more to strings than Unicode, and more to Unicode than utf8. In fact the os does pretty sane here - not checking for utf16 or utf32 isn't really great on Linux either (haven't checked how/if nim handles locales on Linux). Afaik, eg python3 does the right thing on Windows and Linux w/print(). It's just one of the many little things were one may whish for "one, simple, sane way" - but have to deal with the realities.
Same goes for things like handling paths, line endings for text files, resource forks (or not) for files, changing file meta-data...
