I was too, but sounds like the TL;DR is they’re the supporting infrastructure which substack uses:
Substack’s team built its service on Stripe’s infrastructure, which bypassed significant investment in engineering. By leaning on Stripe’s expertise, Substack could scale quickly and focus its energy on fulfilling its promise to writers. The company offers better services because it can continue to lean on Stripe and direct extra bandwidth toward customers.
For me, it was often a place where a lot of qualified people would essentially write blogs because hosting their own site for it would get utterly ignored by google. The last few years though I’ve got more utter morons than people who can write a good article, even for generic questions that they could straight up copy and paste from another site.
While it likely is spam for the majority of users, I imagine the mods are looking at de-federating an instance that fulfills a specific need for a small number (keeping alien.top users updated on reddit). Because of that, it will likely have a bit of push back to de-federate entirely vs. a request to create the ability to block users/platforms. Think of it like newsletters, we need the ability to unsubscribe/block them, but we shouldn’t necessarily ban them outright.
The public part of it would be the RSA pubkey, likely linked with an identifier such as the SHA-256 hash of the email. You could quite easily have that ledger public and it would take millennia to crack any of the emails, much easier to use fuzzing with common words and names than trying wasting computing power for a single email. The whole point of blockchain is that it’s an immutable public ledger which would actually suit this idea quite well.
Not to mention, “You won’t believe this one cool thing!” type headlines (like this one) are classic clickbaiting, and nobody wants to read a 10 page article that’s basically just advertising.