For an rper, i often find the language barrier annoying, since it isn't based on anything more then the childish nature of the wow community throwing verbal abuse at one another cross faction, where as in the lore itself, characters across faction communicate all the time, infact you see it ingame all the time (Genn Greymane fighting Sylvanas, Jaina talking to Thrall, Varian having spats with Garrosh).
But well making across faction communication available to people, I don't understand why we can't have it say ingame in text and emotes, so we can speak to friends who are playing on there opposing faction character.
"Why should they do this, its world of WARRRRcraft" is what your thinking, but honestly, given the state of cross real id allows for communication cross faction with out friend already, it shouldn't really be that much to imagine it happening. Simply allow the jargon to exist with people cross faction if they are not friends, but for people who are friends and in a real id group, they can talk ingame.