The reduction in politeness is also interesting. As someone who really enjoys formality, I like to think that forms are a kind of social guardrail to reduce the likelihood of misbehaviour (which would of course include betrayal), but that's probably far too pat.
Formality won't reduce betrayal but instead prescribe behavior that lets one fully mask intention of betrayal. When expected behavior norms aren't fully prescribed, or when they're impaired (as when one is drunk), it's harder to maintain politeness. Downton Abbey-style formality, on the other hand, lets one maintain the facade of perfect society while stabbing someone's back.
My guess is dehumanization. The betrayer has to shove down their empathy, and that blocks them from thinking of actions that flow from caring about another's feelings - except instrumentally. So direct feeling manipulation, "positive sentiment", goes up.
This may be measuring relative power or favorability of position for the two players. Weaker players are more polite to their stronger allies (and less likely to betray), strong players are less polite and more likely to betray, for example.
I was thinking the same thing. Diplomacy is one of the best multiplayer games ever designed. This should be ideally suited for writing as a mobile app. I'd love to know if there any out there worth checking out.
Maybe, but the related startup idea that came to mind for me might seem
a bit odd; similar linguistic patters might exist in statements made by
startup founders and they might be indicative of success or failure. The
"excessive positivity" and "unnatural politeness" seen prior to betrayal
may also be present prior to startup failure.
The real problem with attempting to prove or disprove this conjecture
seems to be getting the needed data. It might be possible from public
statements from founders, but I think the more significant gems would
only be found private correspondence between the founders and investors
(or possibly customers). I sincerely doubt YC partners or VC's like Marc
Andreessen (@pmarca) and Ben Horowitz are going to let "just anyone" do
linguistic analysis against all of their private personal/business email
content.