This is a soft fork change, which means any single miner can choose to adopt it and remain compatible with the existing infrastructure. Other miners won't add the new transactions since they are "nonstandard", but they will validate blocks containing them.
Can someone explain how this works. I didn't follow it in the paper and I don't have time to read it more carefully right now.
If a new opcode is added for coin return how will existing nodes validate that transactions unlocking coins using an opcode they don't understand are valid?