I think ultimately something like that will be the solution. And maybe it will just be that you can subscribe to any other user's block list, and perhaps they can in turn subscribe to yours, and basically within your peer 2 peer network the block list(s) are federated. You could potentially even have a block and whitelist where when someone you think shouldn't get blocked gets blocked you personally white list them, and in the case of conflicting block and whitelists, a consensus based confidence list is created where some users just don't show in your feed if enough percentage of your block list follows block them vs whitelist them, and users near 50% show in your feed in a collapsed "controversial" mode