This whole thread of comments is full of misinformation :)
It's totally fine to vote on your own posts, and this change has nothing to do with voting on your own posts.
All this means is that for the last 12 hours in the 7 day payout window, no one can upvote that post, people can only downvote.
It creates a 12 hour window that the community can decide if a post was overvalued or abusing the system somehow. Without it, a whale could vote on an abusive post with 30 seconds left and award it $100, without giving anyone a chance to witness/counter that abuse.