I am an ENXX and I get annoyed out of that sort of questions, as I think that non-verbal communication would be best replied by non-verbal communication. Good communicators and observant people do notice such expressions and act appropriately. People can easily follow two communications on the same time, verbal and non-verbal. Taking the non-verbal communication as the topic of discussion disrupts the real discussion.
Extraverts are not looking for verbal affirmation on their non-verbal communication, either. They expect their partrers to do their own thing, whether that is showing a dull face, excitement, or anything.
Extraverts comment on non-verbal clues too, tho. It can be in the form of "oh, you'r THAT excited, uh?" in a light manner. They take the non-verbal clues as communication, if anything. Extraverts also sometimes paradoxically maintain the sense that their whole communication should be regarded as natural, no matter how heavily constructed or acted it really is.
Only extraverts really ever go so hard for the game of pretending, i.e. that I pretend to be interesting and you pretend to be interested, and the weird setup of the situation is not to be commented. The whole game is set up to increase conformity and to gain acceptance, or at least for the practice of skills. The game is lost by breaking the illusion.