Not everyone will do this, or know to do this. nostr:npub1k92qsr95jcumkpu6dffurkvwwycwa2euvx4fthv78ru7gqqz0nrs2ngfwd is examining a solution for iOS Damus.
Discussion
Image analysis is centralizing and not cost efficient. Maybe could crowdsource tag?
Maybe - nostr:npub1yaul8k059377u9lsu67de7y637w4jtgeuwcmh5n7788l6xnlnrgs3tvjmf implemented basic web of trust functionality in Damus.
Early on while nostr is tiny, I question if crowdsourcing can be effective at filtering out adult content consistently. Happy to be proven wrong
What does that web of trust entail?
Last one I saw was Nostrgram but it was more of a view score for indicating how many shared followers you have
It shouldn't imply that all posts signed by a public key are the same kind of content. Accounts should be able to self categorize as sensitive or warning for the content. If other services want to do analysis and clients partner with those services thats all well and good but that cant be the expected approach for nostr as a whole. Clients wanting to moderate experiences should probably not be rendering global by default
Just this for now 
#madethescreenshot
I knew nostr:npub12gu8c6uee3p243gez6cgk76362admlqe72aq3kp2fppjsjwmm7eqj9fle6 was stalking me!
😂