WordPress.org

This plugin auto detects and apply the right direction (RTL or LTR) on post's titles, bodies and comments.

According to WordPress, adding support for language written in a Right To Left (RTL) direction is just a matter of overwriting all the horizontal positioning attributes of your CSS stylesheet in a separate stylesheet file named rtl.css. But this solution is working only when you have just an RTL blog (or just an LTR blog using the classical style.css). One of solutions: We will let WordPress applying the same style.css to both of RTL/LTR posts and this plugin will automatically detect the post language to correct its direction.

It's just a beta version that I tested with the WordPress default theme, please let me know your feedback with your own complexed css.