Ok so as of 4.3 is has been possible to invite other bnet friends to a group and do certain cross realm things with them... but it has NOT been possible to invite another character that is on the same bnet account, when trying to add myself to my friendlist it says "you cant friend yourself"
This puts a damper on certain duel boxing activies that would take place if you have toons on 2-3 different servers.
I BRING YOU A SOLUTION
in 5.0.4 they have introduced cross-realm zones... zones where you can see other players from different realms and invite them to your group etc.. so here is what you do!
1- Log into both accounts (but on the same bnet)
2- Walk both characters to a cross-realm zone (I used the forest outside the main SW zone.. but there is many that work)
3- Get face to face with yourself.. right click and invite!
you are now in a group, that will allow you to do multiple cross-realm activites... but the group consists of 2 accounts linked to the same bnet
This really came in handy when I wanted to have my freind hop in FL and heal on my druid.. but my druid was on the same battle.net account (different realm)