Nothing is stopping anyone from discussing their pay with coworkers (its protected speech) especially in a situation where it seems obvious there is a major disparity or some other weirdness, but I still consider it worthwhile not to idly talk $ with co-workers.
One way or the other, someone is likely going to walk away feeling shafted. And I doubt anyone would be willing to take a major paycut in order to stay on the same level as a co-worker. Everyone just assumes that sharing pay will result in higher pay for everyone.. hello...
It just opens up all kinds of bad workplace issues. Best to leave it be unless it becomes a real issue