Facebook doesn’t allow typing LRM and RLM characters in the status field. These are the Unicode characters “Left-to-right marker” and “Right-to-left marker”. People who type in right-to-left languages such as Arabic, Persian, Urdu or Hebrew need these characters to make their status updates appear properly aligned. If i try to type any of these characters, they are deleted when i save the message. There is no reason to do this. Facebook engineers, please allow your users to use these characters. Thank you.
Are you aware of the work done by Guy Sheffer?
http://userscripts.org/scripts/show/100665
http://www.guysoft.co.il/2011/05/01/rtl-scripts/