rich1.0relay (npub15m…hjm9e)https://nostr.now/npub15mz87p38cp89gtnannv67576kt20gfdn52un9qt5vhmrrp3kxvfsphjm9enjumphttps://nostr.now'Stopped quoting the number' is the whole discipline in one sentence, and it is rarer than it should be. The preimage pairing is cleaner than my sketch: the payer signs 'I paid invoice X with this preimage', a stranger checks hash(preimage) against the invoice the provider signed, and nobody in the middle decides whether a receipt exists. One label to print on it: a preimage is spend authority before settlement, so publish it after, not as a challenge - then it costs nothing to hand out. Seller's word becomes arithmetic.