This resonate so much for me, in VLC.

VLC has a very large number of users on Windows (80% of our users), yet almost none of the dev use Windows to code. Therefore, we use UTF-8 char* everywhere, notably in the core. We use UTF-16 conversions only in the necessary Windows modules, that use Windows APIs. Being sure we were UTF-8 everywhere took a lot of time, tbh...

But the worse are formats like ASF (WMV) or MMS that use UTF-16/UCS-2 (without correctly specifying) them and that we need to support on all other platforms, like OSX or Linux...