True that -- you can only countersignal to people who already know you. But those are normally the only people whose opinions about me I care about (except in job interviews, first dates, and the like -- where someone who doesn't know me well yet may affect me in the future)

As far as first dates go, getting in bad relationship because you are fundamentally incompatible is a lot worse than just not making the second date.

If a woman has a problem with me being nerdy, then it's no problem that the interaction ends at the first date.

On the other hand full openness about who you are is very conductive to building trust and emotional intimacy.

True that -- you can only countersignal to people who already know you.

I don't think that true. If you engage in an action with full confidence and that confidence is clearly visible in your body language and most people who engage in the same action without much social confidence you can counter signal.