I'm preparing to run a game of Bluebeard's Bride with couple of players I don't know very well. This game can be quite heavy on disturbing content, so I certainly plan to have an X-card equivalent in the game. At the same time, I have put a clear indication of the theme and some of the possible triggers in the pre-game blurb (it will be run at a small convention dedicated purely to RPG games), so the assumption is that players will be willing to experience at least some of it and push their boundaries.
As it is a single-session game, in a predefined timeframe (5-6 hours total), there is a limit to how much pre-game 'session 0' research/questionnaires I can do. I also do not expect to have any contact with the players before the game itself.
I'm strongly considering having the equivalent of the O-card in addition to X-card. For people not familiar with the term, here is a definition from TTRPG Safety Toolkit:
The O card can be used at any point if a participant wants to continue with the content. When the O card is used by tapping the card or typing an “O” in the chat, the group is ok to continue with the content. They can also regularly be prompted by a “O?” asked out loud or in the chat to check-in if everyone is still ok.
(Let's ignore the online play part.)
How does it work in practice with multiple players? The X-card is simple - one players bails out, and the scene stops. But with the O-card, is it enough that the directly involved player taps a card to increase/follow the narration, and the rest can X-card it if they don't agree? Can some other players use the O-card, even if they are just listening at the moment? Or do we do a quick vote, which can be quite awkward with 5 players and put a kind of peer pressure on the last one not joining, which those techniques are meant to avoid?