From the fact that you completely ignored the question on whether Nostr has suffered a reality-injecting major problem yet, I assume that it hasn't yet.
BTW IPFS CID isn't even the best, oldest or most stable identifier. We had SHA256 hashes before IPFS.
I answer about things I'm interested in and know about. I don't know about any breaches of Nostr protocol, because I quit all Nostr work 2 years ago.
About IFPS hashing... I'm a very experienced IFPS developer myself (2 years of it). I always argued the 'variable hash algorithm' aspect of IPFS was just an unnecessary complexity and that SHA256 should've been hard-coded into the whole thing. As per usual, the IPFS team went with the more complex approach, just like they did when they over-engineered ATProto in the same way by the SAME developer.
But the main reason Nostr cannot fit into IPFS is slightly more nuanced than the actual hash algo. Fiatjaf made the decision NOT to take the hash of the FINAL JSON object itself, and so no matter what hash algo he had used, it was never going to cleanly fit into IPFS without each Nostr message being 'wrapped' with some IPFS wrapper, necessarily resulting in an DIFFERENT hash. So there's two different layers to the incompatableness.
EDIT: Going deeper into the weeds: If social media messages are shorter than 256K (the default chunker size of IPFS) I think you can end up getting a SHA256 directly out of it, so there WAS the potential to use IPFS with Nostr in that way, except for the fact that Fiatjaf didn't hash the FINAL JSON, but hashed parts of it.
Hey Fraze! I'm a big fan of yours! I bet you know who I am, but don't dox me plz. :) I hope things are going well for you at Blue Sky actually, if you're still there. I think all your contributions to ATProto were probably all the good ones!
I remember Jeromy and his boss Cake who pretended to interview me for a job once, which cratered when I refused to do the "coding challenge" purely out of the principle of the thing. lol.
BTW IPFS CID isn't even the best, oldest or most stable identifier. We had SHA256 hashes before IPFS.