Even if you assume the server operator is benevolent, that would be trivial to fork (and no one should run a closed-source version of that in the first place) b

Even if you assume the server operator is benevolent, that would be trivial to fork (and no one should run a closed-source version of that in the first place) bu someone just forking the extension and using it to trivially DDoS sites for other purposes. Or just break out that part of the code and use it in other malicious client code. Consider also the sybil vector; I could just use a proxy network to vote millions of times for a site I'd like to see targeted. Or how do you ensure that 1 human = 1 vote? Throw in some PoW? No. I'm not for building easily available tools for remotely and unilaterally coordinating DDoS attacks.