There's a social norm in favor of "honesty". And there are in fact social norms for honesty about e.g. who cut down the cherry tree. But not a social norm favoring saying what you think about someone else's appearance.

That's not dishonesty, it's speaking in words which happen to have meanings other than their literal ones. If in a culture people who think X are generally expected to say “Y”, then I'd say that in that culture “Y” means X, regardless of etymology, and it's not dishonest to say “Y” when you think X.