This has to some extent been covered in the following link where hippy did make a start at coding a simple bi-directional protocol (although it is not a complete LEDCOMM protocol): http://www.picaxeforum.co.uk/showthread.php?t=5892
I believe that his code does not implement LEDCOMM completely either, it only shows that the LEDs recognise each other and transmit a sign to the other Arduino that a button has been pressed causing the other Arduino's led to get lit.
Unless you have a high volume cost critical application, I think the IRDA standard would be a better option because it offers more range and higher data rates.