In a lot of campaigns, the PCs are set up to be bumbling fools. Even in the stereotypical "Dungeon Fantasy" games, with bog-standard cookie-cutter expectations players bristle if they don't find, too many GMs set them up to fail, socially. Ignorant of customs the GM mentions only in passing if at all, ignorant of social cues and clues, a great deal of tension, angst and anger is often the result.
Now I think of all the customs and social cues I take for granted, as an American and lifelong New Englander. You drive on the right hand side of the road, and you walk on the right hand side of the sidewalk. The woman in the dark blue uniform, with a holstered pistol and nightstick, wearing a garrison cover and sporting a silver badge, is a police officer. Someone dressed all in black, with a matching high collar with a small white rectangle in the middle, is a Catholic priest. You greet newly met strangers with a handshake using the right hand, and "How do you do?" is a standard opening sally. You cut meat at dinner with your knife in the right hand, transferring the fork back from your left to eat that meat. You don't -- if you have pretensions to courtesy -- wear your hat indoors when visiting; you generally do keep your shoes on.
And so on. So many of these cues are unconscious, reflexive and subtle that we only think about them in the breach. So many of them are also deeply national or regional: not a single one I just listed pertains to traditional Arabic mores, for instance.
The way I see it, not even the best educated and informed among us are natives of the milieus most of us run -- or have worked out in realistic detail what all of the customs are -- and we don't have the level of immersion to notice what someone who isn't a 21st century Westerner gaming out of a comfy living room with a soft drink and a slice of pizza would.
There are any number of times where it's not merely the case that the PC should know a key bit of social/cultural information ("Okay, make a roll against your Savoir-Faire skill ... thankew") but would reasonably know it reflexively, and never normally botch or forget it. None of us need Savoir-Faire/IQ rolls to avoid spitting into open coffins, punching pregnant women in the bellies, saluting the dark skinned archbishop with "Yo, nigga," or failing to understand what the aforementioned blue-uniformed lady with the garrison cover, pistol, silver badge and nightstick is.
So I figure it's my duty to double-check when a player commits what I think is so egregious a social blunder -- well, short of the PC being portrayed as an ignorant lout -- that any informed member of the culture would reflexively avoid it, with a phrase along the lines of "You do understand that this is the Queen's throne hall, and her Chancellor is standing right behind you. Are you sure you want to do that?"
