You don't have to sue all the nodes, just the account that repeats the downvotes. It is simple, Steemit Inc./Steempeak, whatever frontend you use will give up whatever information they have on you and we'll be able to find out who you are. Once that is done its all down hill from there.
Don't think you're anonymous on Steem. You are not.
In fact, all 20 witnesses can be sued. So, they are subject to the laws too. They might one day agree to remove your STEEM from your account. Don't think its impossible, its possible. That's the weakness of DPoS.
If you will recall, there was some pushing to remove STEEM from the Steemit Inc account. It would take a hardfork for that to happen which means the agreement of 17 of the top 20 and someone to actually code that into the blockchain.
As for your premises about lawsuits... that has worked so well on centralized platforms hasn't it? OH wait, hasn't worked at all. So, as I said, good luck with that. You might manage to create a precedent should you try it.
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