By "modus ponens doesn't necessarily motivate," do you mean that someone could see that modus ponens applies yet not draw the inference? That seems correct, but I don't see how this makes metaethical motivational judgment internalism (MMJI) uninteresting. Are you saying that MMJI is obviously false, and so vallinder's point becomes uninteresting because nobody could possibly be that stupid as to come by this route to being at odds with the orthogonality thesis? It seems unlikely that's your point ... everyone who's ever said "nobody could possibly be that stupid" has been wrong (and I'm out to prove it!) ... so then I just don't get it.