The formula for calculating a miner's fee-based score involves both the difficulty score of their share and the transaction fees associated with it. This calculation ensures that a share contributing negligible or no effort (reflected by a difficulty score close to zero) receives an accordingly minimal portion of the rewards. This mechanism underpins the fairness in reward distribution among miners, aligning their compensation directly with their contributions.

Mining pools incorporate a Job Distribution Server (JDS) to validate each share submitted by miners. This system not only facilitates efficient share validation but also includes a lightweight mempool to swiftly identify transactions. In instances where a transaction within a share is unrecognized, the JDS requests the missing information from the miner via a "ProvideMissingTransactions" message, adhering to the Stratum V2 (Sv2) protocol guidelines. The discussion also touches upon the concept of "coinbase-only templates," referring to shares that contain solely the coinbase transaction, effectively acting as placeholders for potential future blocks without additional transaction data.

The complexity of ensuring fairness extends to the evaluation of shares based on the prevailing conditions within the mempool. A discrepancy arises when a share, despite being crafted to maximize transaction fees, is devalued due to a lower than anticipated mempool maximum extractible fees (MMEF) at the time of its creation. This scenario underscores the challenges in balancing reward mechanisms to accurately reflect a miner's efficiency and contribution, particularly under fluctuating network conditions.

A further point of concern arises with mining pools that operate as miners themselves, potentially introducing biases in the processing of transaction fees they generate. Mechanisms for share validation become critical in this context, as they must prevent manipulative practices such as the strategic reordering of shares to favor those with lower associated fees. Addressing these issues necessitates sophisticated solutions, possibly involving adjustments to share timestamps or pointers, highlighting the technical intricacies inherent in maintaining equity and integrity within PoW mining operations.