It bothers me too. It wouldn't be difficult to build a comment self-vote canceler. Maybe there's a whale out there who would be willing to donate some Steem Power to such a project.
If people knew they were risking losing their vote by self-voting, they would self-vote less and go find more valuable things to do with their votes.
If I get time and nobody else beats me to it I'll make a shaaaame bot that reports the worst abusers.
Perfect. It could even include veiled threats of flags. :)