Self voting is usually ok, but if a whale is making hundreds of comments every day and upvoting all of them on the last day, that's a little bit sketchy right?

Last minute votes are generally done so they get the highest possible amount of money, it also usually means the user is just getting the vote for the money rather than the content, which ruins the proof of brain concept that steemit is supposed to run on.

And you do get curation for last minute upvotes, you get 30%.