Anchor Outputs Are a Danger to Mining Decentralization

Since Anchor Outputs are so much less efficient than RBF — about 2x the cost — they pose a significant danger to mining decentralization because of out-of-band fee payment. The problem is that if you have an anchor-using transaction that you need to get mined, it costs twice as much blockspace to get the transaction mined via the intended mechanism — the anchor output — as it does by getting a miner to include the transaction without the anchor output spend.

Some large miners are already accepting out-of-band payments for transactions, allowing you to pay them directly to get your transaction mined; only large miners can reasonably offer this service, as only large miners find blocks sufficiently frequently to make out-of-band fee payments worthwhile. Decentralized mining pools such as P2Pool and Braidpool have absolutely no hope of being able to offer out-of-band fee payments at all.

Since a typical anchor-output using Lightning channel takes 2x more block space, a large miner could easily offer out-of-band fee payments at, say, a 25% discount, giving them a substantial 25% premium over their smaller competitors. Given that mining pool fees are highly competitive, on the order of 1% or 2%, being able to earn a 25% premium over your competitors is an enormous advantage. With Lightning, offering this as a service in an automated, convenient, way would be quite easy to implement.

We must not build protocols that put decentralized mining at a disadvantage. On this basis alone, there is a good argument that V3 transactions and ephemeral anchor outputs should not be implemented.

https://petertodd.org/2023/v3-transactions-review