This is similar to the idea of 'diminishing returns' to make it less attractive to upvote the same authors (including oneself) again and again. I summarized it like that:
"How about if after each vote on a specific account (including ones own account) each further vote on the same account would lead to significantly less curation reward for the voter and less profit for the upvoted account? Thus, when upvoting an account which I had already upvoted before, my voting power would be smaller than in case I upvote an account which I didn't upvote before."
It should also apply for downvotes to make it less attractive to downvote the same person again and again (the idea of downvotes is not to lead personal battles).