Don't forget the case where the two parties are talking at cross purposes (e.g. Alice means that a tree falling in a forest with no-one around generates no auditory sensations and Bob means that it does generate acoustic waves) but neither of them realizes that; it doesn't even occur to each that the other might be meaning something else by sound. (I'm under the impression that this is relatively rare on LW, but it does constitute a sizeable fraction of all arguments I hear elsewhere, both online and in person.)