I upvote my own posts to discourage people from piling on for curation rewards.

Obviously the users are not educated enough to stop voting because of minimal curation rewards...
So my suggestion is when a post is already voted enough and someones wants to upvote it that a message window pops up that sais something like this:

Have in mind that this post is already discovered from many curators and the curation rewards from now own will be minimal for this post! Are you sure you want to spend your Voting Power without efficiency?