IRC is an optional part of OpenSim, see http://opensimulator.org/wiki/IRCBridgeModule
Also, #opensim and #opensim-dev on freenode are OpenSim general support channels which are not grid specific.
Grids like OSgrid operate their own channels like #osgrid on freenode.
But, I understand if you don't want to add it - it was just a thought.
Thanks for reading.
Edit: Oh, to answer your question why would I want it integrated - to provide a central control panel rather than constantly switching from app to app, window to window input box to input box to handle multiple conversations.
Having the IRC channels on freenode IN the viewer would allow more ability to sit inworld and provide Q&A for people in chat AND in IRC together from one "pane" rather than constantly tabbing or mousing from app to app.