Nobody is going to waste their voting power to downvote random people that upvoted their own work and even if they did that's not the kind of system we want to promote where everyone downvote because everyone upvote themselves. It creates a very toxic atmosphere. Linearity has very little to do with self-voting, I have explained multiple times how the curve does nothing to prevent self voting.
The problem you want to solve is a non issue, hardly no one has ever complained about bots having supposedly and edge over manual curator, however if the single vote limit is increased then we create a self-voting and vote concentration problem which will discourage curators and users to diversify their votes and vote for other content than theirs.