Buy in is required to make any externally reacted aspect of a character actually work. It’s a terrible feeling when you’re playing a character who has some externally reacted character trait (usually positive) that nobody reacts to appropriately.
" 1. You owe it to your fellow participant to at least try to play the relationships as designed, of course barring safety issues."
The thing is that while in theatreforms certain relationships might be explicitly noted, and maybe even certain character’s status might be announced, that’s usually only statuses of power. Aspects such as character attractiveness, wealth, fearsomeness, or authority can be unknown, making it harder to play to them. This is even more amplified in player written characters.
Focusing on players who at least want to try to play in, how do we try and convey these aspects?
There’s the obvious, that the player plays towards the characterisitics of the character, but that’s just shifting it back to the acting larper. Additionally, displays might be unwanted, fictionally inappropriate, and actively out of character harmful. I’ve had a character who is supposed to be at least treated with caution if not fear feel flat because it wasn’t bought into, and any display would likely be received in an unhealthy way / I didn’t trust the other players enough to take a demonstration well.
Lists of Dramatis Personae can be one tool that seemed to have moderate success at Scandal and Society, where public information was shared. However, my perception was that only some people bought into that alone, and other buy in was on the strength of the person portraying the character. Of course, parts of that was that S&S has a high romance component, and it is hard to expect many people to buy into romance plots based on characterisation alone.
Possibly a combination of three approaches might work: Dramatis Personae as above, social norming, where people actively step their play to social norm the person who isn’t buying in, and mechanics.
Social norming is as simple as a character who has bought in reacting appropriately to a character who has not bought in, and doing so instead of not interacting. Pulling someone aside to warn them of speaking to the Dread Pirate, Guards hauling the insolent visitor away from the Queen, and people making comments about rich / attractive / powerful person X. It’s what we do out of character, and can easily be done in character if other players are aware and willing to help out.
Mechanics are another area where it can be done, and I’m a fan of building mechanics that support the game you want. If a designer wants to have fearsome character, build a mechanic that plays off that: Consequence and the Outlaw 1 ‘Fearsome Reputation’, which can force another PC to flee a scene is a good example, as was Volcano’s Edge, where Expeditions were locked behind funding on the backing of wealthy PCs. I’m not aware of any around power or attraction, though.
I’m not really sure what to do with people are maliciously, or even just not trying to buy into characters though. I think that’s a much unhealthier situation.