Isn’t that what turn signals are for? Car body language is somewhat location-dependent. Rural Missouri has more cautious drivers and downtown NYC more aggressive drivers. Seems complicated to modify the car’s behavior at such a fine level, but perhaps it’ll happen once the bigger issues are worked out. On-board, personalized learning from your commute would be a neat selling point.

Having driven in the SF Bay with waymo and cruise vehicles - they definitely do signal a sort of extremely hesitant/cautious "body language".

Slowing to a stop in an otherwise clear lane because it's cautious around shadows; Always ceding the initiative on 4-way stops, etc.

It's like there's a (diligent but overly cautious) student driver behind the wheel.

AVs can seem to do that, but it's unintentional. I've never seen or heard anyone describe encoding intent with microbehaviors. The general preference is to make driving intentions as obvious as possible because some people don't pick up on subtleties and we still want to drive safely around them.