Outdated "manners" you'd like to see go away
Nothing is stopping anyone from discussing their pay with coworkers (it's 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 info 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
I can see where you're coming from on this as well. Take me for example. Let's say one other person and me, with the same title, started on the same day and same pay. I'm about to get a pay increase they wouldn't get because I've been doing more than one person's job for an extended length of time. If I don't also get an expanded title, and once my raise goes into effect, let's say we start talking about how much I make versus them, they are going to feel like they deserve more money, too. I personally would prefer the money AND the title but at a minimum I want the pay to compensate me for the additional work I've taken on.
I think that if it's being discussed openly, some considerations would have to be taken when comparing what you make to someone else. Hire date, market value at time of hire date, education, years of experience, span of responsibility, actual job performance, etc.
This is why I said before that people, if they've been at a place for awhile, should advocate for a market equity analysis to ensure their pay is in line with what newer folks coming into the same role are being paid - given that other criteria I mentioned above are similar (education, experience, span of control).