Yeah exactly.
The black one has open o_o eyes but the white one has closed _ eyes
Instead of comparing every single individual users votes with every other one, you create clusters using data science techniques and bucket all users into those clusters, which are calculated on a nightly or weekly basis. By controlling the cluster size you can keep the number of comparisons managable, and still achieve OP’s vision.
You make good points, but I still think nothing good can come of playing ball with Facebook. I dont trust them