What happens if I pay and then someone takes my notes from other relays and throws them into this? That will exhaust my credits? The solution is to require AUTH for publishing such that only you can publish your own notes to this relay. That's built into NIP-70 which is enabled by default on khatru, you just have to require all events to have the "-" tag. Then the question becomes about how to properly publish to this relay, and then we will need some specialized clients or some special relay view section within clients with tools for publishing relay-specific notes.