I love Giacomo and generally speaking I'm a Big Fan. Some of his other tweets... suggest the futility of 'filtering'. NOT that it's bad or the wrong thing to do according to him, but the futility of filtering long term.

The spammers want to do "maximum damage" and they will do whatever causes the most damage - probably 4 mb blocks with lots of unspendable/unprunable UTXOs.

That's why increasing the op_return size won't be used by malicious spammers... because it doesn't do as much harm as stamps/unspendable outputs do.

According to him even a soft-fork/consensus change probably won't be effective... because spammers can easily change and do whatever causes the most damage.

In the long run fee aggregation/L2 fee pressure is the most powerful way to mitigate spam.