I can only speculate as to the motives of the miners doing this, but given OCEAN’s rhetoric I can guess that it has something to do with prioritizing “financial” transactions over others. Even if not, even if it is purely to help small value UTXO owners, it is still every bit as irrational.
You can partition blockspace as a miner however you want, and prioritize ordering of transactions however you wish within those partitions, but it does not change the fact that blockspace is a fungible good being valued on an open market. If criteria other than the feerate are used to decide which transactions to include, you will leave money on the table. The only situation where that would not be true is one where those criteria were 1:1 identical to deciding based on feerate, which would be a meaningless criteria.
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