> The sheer volume of spam or even just angry/abusive users on public platforms these days is hard to describe if you haven't been on the spam/abuse prevention side of a popular website.
I haven't been on one of those teams, so I hope you'll forgive the naivety, but:
These seem like solvable problems with decentralized systems. In both cases, someone has to go through the work of manually identifying the bad content, right? In a centralized system, that's someone working for the system - in a decentralized system, that's a random user.
From a technical perspective, then, the centralized "please delete this content" message is pushed out the entire system, while the decentralized message/action can be put into a blocklist/banlist that other users can subscribe to. I believe that this is how the Fediverse works, for instance, and it's definitely how adblocker blacklists work - so this kind of system is already in effect, and seems to be working decently.
If the volume of spam is truly extreme, then what's to prevent you from having distributed blocklists that are fed by automated processes (as opposed to manual additions), and users just subscribe to the ones that they trust?
From a social perspective, users seem to be willing to do this work themselves, given how driven the users of sites like Reddit are, with no more reward for posting high-effort content than a bunch of imaginary internet points, and how effective adblockers are.
To summarize - what prevents a decentralized system from taking the same approaches that a centralized system would employ, packaging them into blocklists, and then allowing users to choose which of those they employ? Same tech, different level of control.