alt Hacker NewsOf the two UTF-16 is much less of a problem, it's trivially[1] and losslessly convertible.
[1] Ok I admit, not trivially when it comes to unpaired surrogates, BOMs, endian detection, and probably a dozen other edge and corner cases I don't even know about. But you can offload the work to pretty well-understood and trouble-free library calls.
It causes such issues as opening of files by filename not being cross platform with standard libc functions since in Windows w-string versions are required since UTF-16 chars can have 0-bytes that aren't zero terminators