Let me see if I understand correctly: Client takes its own public key and the server's public key and creates this signature.
MITM can take its public key and the client's public key and send the resulting signature to the server instead of forwarding what it received from the client.
Do pretty much the same exact thing: MITM PK + Server's PK -> Client. Now client has a signature as well. The signatures that client and server have are different but that is OK as long as MITM can see and change all communication.
It has been a while since I went through the details of the protocol, so I must be missing something. What is it?
How can you then turn around and try to mask it as "citizens supporting their political goals"?
Clear communication points released from headquarters to all the media minions, social media platforms, election influencing channels, and on and on.