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

The mempool serves multiple vital functions beyond just enhancing block propagation. It plays a crucial role in enabling nodes to validate transactions, cache signature validity, and update the UTXO set efficiently. However, the use of filters can negatively impact these processes. The user experience significantly suffers when processing an entire block of transactions results in noticeable computer slowdowns and network congestion. Such scenarios have been observed to cause disruptions in other network-reliant services like video streaming due to the heavy data load every 10 minutes, which was a common issue before the introduction of compact blocks.

Despite potential strategies to influence miner behavior, non-mining nodes face limitations in their ability to enforce rule compliance among miners. The only practical leverage they might possess would be coordinating a fork to amend consensus rules. This dynamic underlines the inherent challenge in attempting to regulate miner actions strictly within the framework of existing network rules.

Furthermore, the effectiveness of mempool policy as a deterrent for transactions that violate network rules is questioned. An argument is made against the assumption that such policies are highly effective, suggesting that without significant economic disincentive, transactions disregarding these policies will continue to be produced and included in blocks. This perspective challenges the notion of filtering mechanisms' utility, implying that as long as there is economic motivation, undesirable transactions will find their way into the blockchain despite policy barriers. This discussion points towards a reconsideration of certain filter applications, emphasizing the need for more nuanced approaches to managing transaction policies within the blockchain ecosystem.

For further information and insights into these discussions, Andrew Poelstra’s work can be explored through Blockstream Research at https://www.wpsoftware.net/andrew.