In both cases you will know the difference, just not immediately.
Certainly it would not justify something as cynical as this:
> "Aren't most people just failed social actors who are rather poor at picking the signs in which to display their emotional communication?"
which was the part that really rubbed me the wrong way.
But, aren't they?
Not actor in the sense of a script/a lie, but in the sense of trying, ultimately imperfectly, to convey how we feel to the world around us?
How often do you think you nail the perfect smile, the perfect handshake, the perfect snuggle, to demonstrate happiness, but not too much, familiarity and strength without being overbearing, and tenderness without clinging?
Combine that with the imperfect feedback you get from others and we have really have no idea about the finer details of anyone but yourself.
Not just that you can't detect lies but that we have no way of telling if our perceptions of red are the same, let alone a hug or a complex thought.
It seems to me (perhaps this is a misreading of the post) would have us dismiss emotional expression as inherently untrustworthy, or somehow unreal. I disagree vehemently.
Sure, our expressions, and the way they're perceived, is colored by brain chemistry, social conditioning, and a myriad of other factors... but I maintain that it simply makes them more complex, not less real.
There is a broad range between trying imperfectly and being a failed social actor.
@potatolicious is comparing the experience of a tasty meal to the experience of love/happiness/whatever, and saying that it doesn't matter what the underlying cause of it is, it's the experience that matters. I think it's a reasonable point.
You're saying that the experience could be 'fake' because it's based on a fake stimulus. Just in the same way that a loving experience is could be based on a fake interaction by someone else (say a psychopath).
But from /your/ perspective, is there a difference in the experience between the fake and the real? If the inputs are the same, the experience is the same, whether they are triggered by chemicals or some kind of higher-level mental state that we can't adequately explain via chemistry or biology.
The OP seems to be denigrating the human experience based on the chemical 'fakery'/self-deception involved. But that's a different kind of fake--that's your body 'faking' it. [And I totally disagree with that by the way; I agree completely with @potatolicious].