OK, I agree with this: "...that removing the rewards on comments is a first and necessary step."
Sock-puppet creation is too easy for this to be a viable total solution, but it sends a message to the copy-cats.
Indeed, if the only logical reason to self-upvote a comment is for promotion, then it logically should cost a bit to do so. This may not be visible in dollars bit can be adjusted in the Vests value.
Good point but you know that many people feel they have already purchased this right by buying STEEM and powering it up.