Thanks, I was half getting the point, but is this really important, as you say? If my goal is to gain value by assessing whether or not your proposition is true, why would this matter?

If the goal is to learn something about the person you are arguing with (maybe not as uncommon as I'm inclined to think?), then certainly, care must be taken. I suppose the procedure should be to form a hypothesis of the type "Y was stated in an inefficient attempt to express Z," where Z constitutes possible evidence for X, and to examine the plausibility of that hypothesis.