I don't know much about language support, but if you know HTML or Markdown, the following are some great distraction-free text editors that I personally like to use a lot. Although, I know for a fact that they support at least Greek and Japanese if you enable their respective keyboard layouts because I've tried it.
Take note that they aren't really word processors in the typically used sense since they're WYSIWYM ("What You See Is What You Mean") rather than WYSIWYG ("What You See Is What You Get"), but if you know HTML or Markdown you can very easily use them for all kinds of documents. I do all the time. (Even though they're text editors, they do have support for various font styles, serif and sans-serif alike.)
If you like Markdown, the following are some distraction-free editors that I suggest you might try out. I haven't really used them that much as I've only installed them both today, but so far they seem to work really well, so it might be something you may want to at least try, eh? :)