Relax OP_RETURN standardness restrictions

The discussion centers on the dynamics of block propagation in the context of Bitcoin mining and how miners handle transaction data. It highlights a nuanced aspect of blockchain technology, especially focusing on the relay of compact blocks and the validation process. The capability of miners to delay the broadcast of a block or withhold transactions is not fundamentally different from their ability to delay the entire block, with the primary distinction being network visibility. This visibility pertains to whether a miner chooses to delay broadcasting a block until they have completed preliminary validations up to the BLOCK_VALID_TRANSACTIONS stage.

A critical point raised concerns the propagation of compact blocks within the network. Currently, the reception of a compact block by a miner is contingent upon every node along the path having all necessary transactions locally. This setup inadvertently slows down the block propagation as nodes missing any transactions delay the process. The proposal suggests that minimal validation, including proof of work, header, and merkle root checks, should suffice for the relay of compact blocks. This approach would enable miners to receive compact blocks without delays caused by missing transactions, thus streamlining the validation and mining process.

Moreover, the discussion touches upon the decision-making process miners undergo when encountering new blocks that they haven't fully validated. Miners must choose between starting to mine an empty block atop the new one or continuing with their current work until validation is complete. This decision-making process is part of the inherent flexibility in mining operations, underscoring the strategic considerations miners face in optimizing their efforts.

Lastly, the conversation delves into the topic of transaction relay policies and the diversity therein. It argues against the necessity for a uniform relay policy across the network, citing the example of full-RBF (Replace-By-Fee) to demonstrate that a variety of mempool policies can coexist effectively. By granting users more control over their node's relay policy and encouraging a shift towards more permissive policies, the system can maintain efficiency in transaction relays to miners. This perspective advocates for a decentralized approach to policy management, reflecting the broader ethos of the Bitcoin network and its underlying principles of autonomy and distributed consensus.