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Anime avatars are often a coin toss between (potential) comrade and chud, so it may be fun and maybe helpful to think about and share those in the place of that old 
bellwether for chuddery.
Mine is anyone with ".eth" as a suffix in their online name. I have yet to see a single person that does that that isn't a chud. 
It may even be cheating, but seeing an actual cryptofascist cartoon "original NFT do not steal" is a pretty reliable red flag too. 
EDIT: Oh yeah, I almost forgot. 
yeah I mean I wouldn't build a 'Chud-o-Meter 3000' around this because some people are collectors or want to be well rounded, but companies that print these usually choose from the western canon, so no radical stuff allowed, I have a few general history books bound in that classic style but nothing left-leaning except for the Eric Hobsbawm Modern History series.
I'm more thinking of people who show them off in the background as part of their online persona like some right wing commentators
It's not about the content of the books for me. It's about the smell