I dont know who this message is to go to, but whoever is in control of the translate project for wordpress should read it. Someone has already made a whole translation for wordpress (which you can install if you own your own server) so I dont know why wordpress.com doesnt know about it. If you do a simple search for "wordpress" and "japan" you get hits to a site called....go figure...Wordpress Japan with a full translation.
So just take that file and put it in the wordpress.com API already, i know tons of japanese that want to but cant use wordpress.com for a blog cause its not supported yet (even though its been done for awhile). yea so please tell the relevant parties. thank you
(heres the link page of the zip files on sourceforge.com that update wordpress [for those who cant read japanese])