@prabe @billd91 @Fanaelialae
I personally find that level of group coordination extraordinary. I do not think it should be taken as a given.
For my part a good deal of how I learned to run games is focused on getting players to play their characters as individuals. If a character is present on the scene during a social interaction I would expect that they would be actively involved in the negotiations. If they were not NPCs would bring that up. I might also ask them questions about how they see things.
Now if they are like not in the scene because they are doing other things or are on the other side of the room that's one thing. If they interrupt when I am specifically addressing someone else that's another. If your character is physically present you are in the scene.
Of course at the end of the day a lot of this confusion comes from the lack of instruction provided to players and GMs by the game. There is no meaningful sense of where your priorities ought to be so unless that is resolved by group explicitly you are apt to run into mismatched play priorities.
You're arguably right. My group certainly wasn't like that when we first got together something like 20 years ago. It was something that developed over time, and was nurtured in newcomers as they joined our game.
That said, I don't think it's an unreasonable thing to expect from mature players (if they're teenagers or something, it probably is entirely unreasonable). That's not to imply that not playing this way is immature. Mature players might enjoy non-cooperative play, and if that's their dynamic then sure, why not.
I mean, to me the fact that you should play a cooperative game cooperatively is not that much different from being aware that you shouldn't "accidentally" trip your own teammates in basketball just because you want the ball to be passed to you. It's not obvious to everyone, but I feel like for most people it is reasonably intuitive. Even back before we reached our current level of coordination, there was a general acknowledgment from most players that antagonistic play wasn't... ideal. If only because it tended to cause real world arguments and bad feelings.
It's one thing for the players to riff off each other and decide that the barbarian is going to cut the boring negotiation short by attacking the mad tyrant. It's another thing for the barbarian to pull the rug out from under the negotiator by ruining a scene that the negotiator was engaging with. Even in groups where players don't side bar to come to an agreement on the direction to go, you still often see this kind of play. It might be the DM looking at the other players and asking "are you going to let him do that". Or the negotiating player might look at the barbarian player askance and say, "come on man, let me do my thing". Certainly not every table does this, but I don't think it's a rare playstyle. We just cut out the risk of clashing egos by having a polite OOC conversation about it, which is a slightly more direct way of going about the same thing.
That the party knows about.
Only an idiot PC would break a party's trust in such a way as to allow the party to find out about it.
Then again, look at the first three Pirates of the Caribbean. In the end nobody trusts anybody in that series, but when they have to they work together - until the danger has passed at which point they stab each other in the back. Great stuff!
"I'm not sure I want rescue from you lot. Four of you have tried to kill me in the past; one of you succeeded." - Jack Sparrow, while in Davy Jones' locker.
No, because either it's such a trivial act that no one cares, or it eventually comes to light, at which point the only reason they stick together is that they're PCs (or the equivalent of PCs in the case of the pirates movies, which I've watched because my wife likes them but aren't exactly my favorite movies).
We once played an evil campaign where one of the players was a homebrew torturer class who could make a person or animal into their minion by breaking their will. My character was a medic who always found the good in everyone, especially those who didn't deserve it, and was also the leader of the party. The torturer played it up that he had rescued his minions from terrible conditions (explaining the injuries he had inflicted). It worked as an excellent dynamic at the table, and everyone was greatly entertained. But the thing is, he wasn't acting against the party's interests. He was simply doing his own thing, which might have caused the party to view him in a different light had it been known. Even had it come to light, my character would have argued his case since he was the worst kind of apologist.
Contrast that with another guy in that same campaign, who was jealous that I was party leader (it was determined by a homebrew reputation system, but I honestly never used it to force anyone to do anything). Ultimately, when it became apparent that he couldn't seize the leader position, he tried to get my character killed and instead caused a TPK that ended the campaign. We don't game with that guy anymore. We used to be more tolerant but eventually came to the conclusion that we don't get enough game time to waste it with people who are willing to ruin everyone's fun for their own selfish reasons.
YMMV