Isn't the language code for Japanese JA? So, in the drop-down menu, info from Japanese Exchange comes up with a little icon that says "JP". What's that all about?
I'm not sure why it says JP.
Both JA and JP are fairly common abbreviations. Officially, JA is the ISO 639-1 language code for Japanese, while JP is the ISO 3166-1 country code for Japan. I think both are understandable, and obviously Japan and Japanese are very closely associated, but since the site is about the Japanese language and not the country of Japan it might make sense to use JA instead.
Darius Jahandarie wrote in chat:
I wanted to say that "JP" is a far more common abbreviation for anything related to Japan than "JA". Only computer programmers know about "JA".
So this would be an argument to stick with JP.