Good point. If the main function would be implemented on all nodes and everyone would exchange information (hashes), which elements are harmful, we would maybe have a chance to skip central nodes from the equation. If the information is distributed throughout multiple maybe random nodes, but this would pose new problems - where to find that information.

I believe if users are empowered to participate in combating the problem, almost all users would. The question is, how can the nodes harvest this? What can ordinary users do to help?

I agree. Maybe the node can create some "unsafe" hashes and share them between the nodes - kind of like an antivirus creates hashes for malware. The user can always report to the admins - when there are more instances there are automatically more admins to handle the request themselves or with bots.