The sender can pay without spending another on-chain coin, and the receiver keeps almost the whole payment.

I'm trying to think through whether this has other benefits. I have been in a situation where I had a utxo that was the right amount for a gift, but the transaction fee made it into an ugly number (this is a relatively trite concern, I realize), but are there other situations where it is beneficial to avoid splitting a utxo to pay to the mining fee?

Here's the @1440000bytes longer description:

• Zero-fee sends. The sender signs a payment that pays no fee and passes it to the receiver over Nostr. The receiver attaches a child transaction and broadcasts both together as a package.
• Pay the fee off-chain. The package goes out at the minimum fee rate (0.1 sat/vB, about 31 sats for both transactions), and priority is paid over Lightning through the mempool.space Accelerator, straight from your wallet with Nostr Wallet Connect. The sender can pay without spending another on-chain coin, and the receiver keeps almost the whole payment.

I enjoy curious bitcoin things like this. Great job, floppy.