Antiversation? Altiversation?

Does it have to be an anti-conversation? No, you mention alternative. But, does not "additive" a good word here? Super-imposed.

A simple example: Let's say we watched a TV show, and in our own homes used IRC to dig up facts about stuff that was shown in the TV show (say, using Wikipedia links, or just noting connections you come to think of). Things like CSI could be more enjoyable, or any old techno-thriller, or political thriller. "The real story, while you watch the representation."

(Product idea: IRC for Picture-in-Picture on large screens.)

If everything comes with a backchannel, should everything also have a terminal? A hackable mode.