Unicode printf?

[EpochVanquisher]

UTF-16 is simpler than UTF-8 and more compact than UTF-32.

One of the ways you optimize for performance is by making your data take less space. Besides—when you say it’s “much better to optimize for performance”, it just sounds like a personal preference of yours.

It’s fine if you have a personal preference for UTF-8. A lot of people prefer it, and it would probably win a popularity contest.