The other element to this is it illustrates that politeness is a function of power and privilege. Joyce can afford to be affable to whomever she wants because she has nigh unlimited resources and a private army and is capable of doing whatever dirty work needs done out of the collective eye (Capital only has to drop the mask for an instant). Claire also dissembles and uses people to accomplish his goals, but it's because he has to outmaneuver an opponent with superior resources and institutional power. He's easier to "see through" than Joyce because he works out of a shipping container rather than a fancy boat and would look silly trying to talk and act like Joyce. He has to fit into his milieu.

There's something that's removedled at me ever since I wised up to the fact that politeness is used as a weapon to stifle dissent. At first I thought it arose as an unconscious reaction because people instinctively realize that it reinforces the status quo, but seeing politicians constantly harp on politeness (even otherwise abrasive assholes like many republicans), I've come around to the idea that the wealthy have always understood its role as a weapon. I know most politicians come across as idiotic and tone deaf, but you don't get to national office without understanding that people are malleable and tend to reflect whatever energy you put out. Smarm is kind of a poor man's version of that, the double bluff where you can't fake sincerity but you can come across like you're acting like you're faking. The game does a good job of illustrating it by putting you on your back foot with the negotiations if you accept the giant novelty check.

When it comes down to it Evrart and Joyce are converging on similar psychological principles but from opposite ends of the sociopolitical spectrum.