How Does a Zero-Fee Transaction Affect the Profitability of a Mining Pool?

A zero-fee transaction slightly reduces the profitability of a mining pool compared to including a fee-paying transaction of the same size. Since block space is limited, including a zero-fee transaction means forgoing the potential revenue from a transaction that would have paid a fee.

While the impact of one zero-fee transaction is minimal, a pattern of including them would reduce the pool's overall revenue and competitiveness.