Ephemeral Anchors and MEVil

Protocol Design
6

So there is one remaining oddity even with the diagram based “anti-MEVil” check:

There is still an additional incentive for someone to ramp up the ephemeral anchor value(if another party is paying), if the additional satoshis can be used to have the child conflict with another transaction in the case where the other transaction is a bip125 rule#3 pin.

Example where Bob uses Alice’s trimmed funds to pay for conflict against TxD:

flowchart TD
    A[TxA: fee 1\nsize 1] --> B[TxB: fee 5\nsize 1\n conf TxC]
    A --> C[TxC: fee 106\nsize 1]
    D[TxD: fee 100\n size 100\n conf TxC]

This oddity only exists due to anti-DoS rules, otherwise there’d be no (additional)incentive to do this as the adversary is only increasing their own required child feerate.