No. Any valid string is a valid key. It can even have "
as long as you escape it:
{"The "meaning" of life":42}
There is perhaps a chance you'll encounter difficulties loading such values into some languages, which try to associate keys with object field names. I don't know of any such cases, however.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…