[wp-polyglots] using xx_YY.php in translation files for setting directionality

[Ran Yaniv Hartstein]

I can't find proper documentation in the codex for setting theme
directionality and for other uses of the xx_YY.php file in the
translation files.

This article by Ryan Boren is the only reference I found on the
matter, and it doesn't fully work for me:
http://boren.nu/archives/2007/01/07/rtl-support-in-wordpress-21/

The install procedure and error message contain functions to be RTLed
according the the text_direction variable, but they just don't work.

Also, there is no documentation on how to use xx_YY.php file to change
features in wordpress as a substitute to a plugin. For e.g., I have a
filter plugin I want to include in this file. How do I go about doing
that?

-- 

--RYH,
www.trans.co.il