Exactly. And that's not even following the "web of trust" model. It's just straight up shadowbanning.
Discussion
I think spam is a difficult issue as it's subjective. Using nostr:npub1nym2200088t397yx43lza4gfec3rk56gxnwjnk2u4w5ld0qpau6sskc7fq as an example, my guess is he got caught in the amethyst spam filter twice. 1 he regularly posts the same "what's for supper ..." message which I believe nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z has said amethyst blocks accounts with the same post multiple times. 2 at one point he was zapping 1 sat to every post which some people complained about and likely blocked him for. While I don't consider either of these spam and actually like to see them, I can see how some may call that spam. Which is why I think the current amethyst spam filter while well intentioned without being able to opt out is too far. I respect Vitor's position that software should be opinionated, and that open source allows it to be forked. In relatively new ecosystem like this I think it's healthy and in the long run will lead to the best software and user experience.
I think you hit the nail on the head. And it demonstrates the difficulty in general that any software has in balancing out blocking clear cut obvious spam (e.g. those Optimism messages) and genuine users whose activity happens to trigger an algorithm.
And all fairness to nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z I've spoken to him about why one of my accounts, nostr:npub1ms4z8e2fsgjh75vtk8c9pym50gjvp3uxl7uru8v7c7pnd9empadq2ulevr, got caught up as spam in Amethyst and he was very transparent about it and helped me remedy the issue (which I've since done - it used to post duplicates, but now I've updated the code so it has to run through the full list once before it starts again, and put that code on GitHub).
He's definitely taken the fairest approach possible, although I'm not sure why nostr:npub1nym2200088t397yx43lza4gfec3rk56gxnwjnk2u4w5ld0qpau6sskc7fq is still blocked when many on Nostr enjoy the excellent AI art he shares.