If I understood you correctly, I think that people do do this kind of thing, except it's all nonverbal and implicit. E.g. Using hard to fake tests for the other person's decision theory is a way to make the other person honestly reveal what's going on inside them. Another component is use of strong emotions, which are sort of like a precommitment mechanism for people, because once activated, they are stable.
Yes, I understand the signal must be hard to fake. But if the concern is merely about optimizing signal quality, wouldn't it be an even stronger mechanism to noticeably couple your payoff profile to a credible mechanism?
Just as a sketch, find some "punisher" that noticeably imposes disutility (like repurposing the signal faker's means toward paperclip production, since that's such such a terrible outcome, apparently) on you whenever you deviate from your purported decision theory. It's rather trivial to have a publicly-viewable database of who ...
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: