[astrange]

Swift originally had UTF-32 strings (an upgrade from ObjC which uses UTF-16), but they redid String to be UTF-8. It's typically the best choice even for CJK text, because it has ASCII mixed in often enough to still be smallest.

I don't think reversing a string is a meaningful operation though; there's no reason to think of a string as a "list of characters" when it's also a "list of words" and several other things. Swift provides more than one kind of iteration for that reason.