[BIP Proposal] Mempool Validation and Relay Policies via User-Defined Scripts

In the recent discussions on the Bitcoin Development Mailing List, several key points were raised regarding the effectiveness of filters, censorship through the adoption of filters by a majority, and the distinction between filtering arbitrary data and censoring consensus-valid transactions, such as those compliant with OFAC. The debate touches upon the complexities of combating spam within the blockchain network, emphasizing that changes to consensus rules are not a viable solution for stopping spam. Instead, implementing policy-based filters is suggested as a more effective measure to increase the difficulty for spammers.

The conversation also revisits historical perspectives, notably Greg Maxwell's invocation of Satoshi Nakamoto's approach to policy implementation to prevent specific scripts from being included in blocks, highlighting a foundational precedent for policy use in network management. This point underscores the ongoing tension between preserving the decentralized ethos of blockchain networks and the practical need to manage network health and security through some form of intervention.

A significant concern is the perception of miners' role within the network and the impact of their actions on node operators. The discourse criticizes the notion that miners have control over the network, suggesting instead that a more balanced view should recognize nodes as independent agents with the autonomy to determine their mempool contents. This perspective advocates for a model where miners are responsive to the relay network's mempool, ensuring alignment between what is relayed and what is mined.

The discussion culminates in the presentation of a Bitcoin Improvement Proposal (BIP) aimed at finding a middle ground that respects the autonomy of node operators while addressing the challenges posed by spam and unwanted data within the network. This proposal is seen as a step forward in the ongoing effort to balance the principles of decentralization with the practical necessities of network management and governance.