Are strangers sincere in their moral praise and criticism? Here we apply signaling theory to argue ceteris paribus moral criticism is more likely sincere than praise; the former tends to be a higher-fidelity signal (in Western societies). To offer an example: emotions are often self-validating as a signal because they're hard to fake. This epistemic insight matters: moral praise and criticism influence moral reputations, and affect whether others will cooperate with us. Though much of this applies to generic praise and (...) criticism too, moral philosophers should value sincere moral praise and moral criticism for several reasons: it (i) offers insight into how others actually view us as moral agents; (ii) offers feedback to help us improve our moral characters; and (iii) encourages some behaviors, and discourages others. And so as moral agents, we should care whether moral praise and moral criticism is sincere. (shrink)