The data validation concern seems fair enough. > Almost all application programming languages use utf16 anyway, (javascript, c#, swift, Java) Swift 5 switched

The data validation concern seems fair enough. > Almost all application programming languages use utf16 anyway, (javascript, c#, swift, Java) Swift 5 switched to UTF-8: https://www.swift.org/blog/utf8-string/ https://www.swift.org/blog/utf8-string/. I’m hopeful that other UTF-16 environments might eventually manage to switch to UTF-8 internally despite retaining some UTF-16 code unit semantics for compatibility; two projects have already demonstrated you can very practically do this sort of thing: Servo from fairly early on (WTF-8 despite the web’s UTF-16 code unit semantics), and PyPy since 7.1 (UTF-8 despite code point semantics, not sure what they do about surrogate code points). I know the web has largely backed away from UTF-16 and uses code point semantics (well, scalar values plus loose surrogates) on almost all new stuff, with good UTF-8 support too.