A better way for tipping to work on nostr:

When you enter your seed words, any app you'd enter them in also saves the seeds for wallets for various cryptocurrencies.

For fixed-address cryptocurrencies such as Ethereum, the wallet address is added to your profile if you choose to include it.

For rotating-address cryptocurrencies, clients are configurable so that they automatically respond with a wallet address if they receive a message containing 2 deltas ∆∆ followed by a space followed by a ticker symbol. This format is so simple you don't need an example to be sure you understand it, and it should never be needed for another purpose that makes anyone frustrated by the automatic replies. Requiring wallet addresses to be requested with a message helps avoid promoting address reuse for UTXO cryptocurrencies such as Bitcoin.

Profiles should have the option to include a tipping address, which is a separate npub these address requests can be directed to. The separate npub can be a third-party service which is fed new wallet addresses when the user is online for their client to periodically update the list. The third-party service wouldn't need access to the wallet funds or seed in this case, a signer app like Amber would be generating the wallet addresses. The separate tipping npub can also use separate seed words to generate wallet addresses, which helps if the user wants to keep the money-storing seed more secure than the seed they sign posts with.

After receiving a wallet address, a tip-sender can tip without any more involvement of the nostr protocol, or they can broadcast an event recognizing the tip (similar to existing zap events).