Lets you copy characters that are the same (like people's names) between text though.
People's names are the thing you should be most careful to not do that with! Most Japanese people will generally put up with seeing the Chinese rendering of a character in ordinary text, but they really don't want you to do that to their names!
Sure. And once you're doing that you don't gain a lot of benefit from unicode AFAICS, because you have to track these spans of locale-specific text.