Why do some browsers seem to require a UTF-8 charset on JSON data for display?

Question

So I see the A: What is the correct JSON content type? - application/json as well as Why content type header to use for json? "application/json; charset=u

Answer 1

There is a Firefox bug on this: "Don't honor charset when viewing JSON" #741776 says that XHR ignores charset and that docview shold also.