Firstly, when you said "'I'm claiming that there is no reaction I could have which would cause you to think that you'd said the line differently" I thought you were using the general "you" (in the sense that we couldn't imagine any reaction that would lead me, the speaker, to think I'd said the line differently). So I acknowledge that it wouldn't really be your reaction, and it wasn't my intent to suggest it.
I didn't think you were. Honestly, your approach to language is so alien to me that I often don't foresee your interpretations.
Which, I think, only serves to reinforce my point. We don't all use language the same way, and as such we cannot reasonably expect to be able to predict the reactions of someone else.
Secondly, your non-response would absolutely make me thing I failed say what I wanted. In the original example, if I made a really cheerful greeting and you didn't react (or reacted absently), I'd think you didn't get my meaning (or weren't paying attention). The intended outcome of the line wouldn't have it's effect, so that would tell me there's a mismatch and I need to try something else to get the effect I was attempting to get.
Those are two different things. Are you saying that you would question whether you said what you meant to say, or that you would want to try to say something else to achieve the same results?
I'm talking about the former, not the latter.
The key thing to appreciate is that, again, it doesn't matter to me whether you actually perceive my meaning as I internally perceive it. That what is sarcasm to me is cheerfulness to you is irrelevant if - for all possible observable and practical purposes - you respond to my sarcasm as I predict and expect. It's a purely instrumental theory. To use a science analogy (which Bas Van Frassen likes quite a bit) even if all our theories about science are completely wrong, it doesn't change the fact we build very good ipods.
It's for this reason that Huygens's description of diffraction has always bothered me. The math works, sure, but the explanation is laughable.
The bold is plainly wrong. The whole point of a shared culture is that we can do this, because we all internalize similar reactions to cues, stimiuli, etc. You're confusing "reliably" with "perfectly".
It's a difference of scale. That I can predict with some accuracy how a population will behave does not grant me the ability to predict the behaviour of an individual, particularly exceptional individuals.