Hi Dexmaster,
Thank you a lot for the testing and feedback.
From info I googled here in the forum, RTL is not supported in KOReader because CREngine doesn't support it. Here's a ticket in CREngine bug tracker:
http://sourceforge.net/p/crengine/bugs/32/
Obviously there's no plans to support RTL in Cool Reader, and it means KOReader won't support it too. This is how I understand the situation.