Morality is not just social signalling, because it makes sense to say some social signals (“I am higher status than you because I have more slaves”) are morally wrong.
That conclusion does not follow. Saying you have slaves is a signal about morality and, depending on the audience, often a bad signal.
Note that there is a difference between “morality is about signalling” and “signalling is about morality”. If I say “I am high status because I live a moral life” I am blatantly using morality to signal, but it doesn’t remotely follow from that there is nothing to morality except signalling. It could be argued that, morally speaking, I should pursue morality
for its own sake and not to gain status.
That conclusion does not follow. Saying you have slaves is a signal about morality and, depending on the audience, often a bad signal.
Note that there is a difference between “morality is about signalling” and “signalling is about morality”. If I say “I am high status because I live a moral life” I am blatantly using morality to signal, but it doesn’t remotely follow from that there is nothing to morality except signalling. It could be argued that, morally speaking, I should pursue morality for its own sake and not to gain status.
That sounds like an effective signal to send—and a common one.
Noted yet not especially relevant to my comment.