I generally consider "you ought to do X" to mean "I'd prefer it if you did X", and do not think judgements of "ought" can be wrong in this sense. (Aside for the normal questions of "what does a preference mean", but I don't find those relevant in this particular situation.) I agree that there are definitions of "ought" by which moral judgements can actually be wrong.

Incidentally, since I just read your comment over at Remind Physicalists where you pointed out that upvotes (or by extension, my "great post" comment) don't convey you information about what it was about the post that was good: I found the most value in this post from the fact that it made the general argument of "our moral arguments tend to be rationalizations" with better citations and backing than I'd previously seen. The fact that it also made the case of deontology in particular tending to be rationalization was interesting, but not as valuable.