Lol. PoW exists to make it hard to rewrite history, not to prevent spam. This is obviously just more dishonesty masquerading as "bridge building" after a week of non-stop character assassination after many months of bad faith interaction. Citing your credentials "I have worked on anonymous systems for over a decade. I have read tons of research on spam detection, rate-limiting, and I've implemented spam prevention techniques in the real world." ...is not enough to make people pretend you're arguing in good faith here which you obviously aren't having opened with rewriting the entire function of what PoW does and how Satoshi used it. We know specifically what Satoshi did about spam and you're ignoring it because that would contradict your premise. (Further - spam filtration does not imply centralization. The opposite is the case. No one is going to run nodes if they do not posses the tools to prevent their mempools filling up with porn/malware and anything else that can leverage the idiocy of Bitcoin's developers.)