The install script contains a zip file that actually installs EVERY LOCALE (it unzips them all onto the kindle, but then deletes them all except the zh_CN one) and uses that locale.
IDK enough about locales but you can mess with it if you do. Also don't know about incompatibilities with the reader. The files are in the word.tgz file or w/e it is called. you can see the file in their update packages. It deletes it after you run the software update to a new version. I guess if you want you could just edit their script to not delete the other locales and then telnet in and set different locales or w/e you want.
http://www.linux.com/archive/feed/53781
locale is just date/time stuff. Actually why the hell is it setting our stuff to Chinese locale =(
Guess it doesn't really matter but.. why?
This doesn't have anything to do with languages..
Pretty sure their reader is broken and only using the standard limited ascii set. Which is probably hard coded into it.