I haven’t seen it announced anywhere, but Tumblr recently made a couple of changes to the way reblogging works. You can now reblog any post, including your own — “Reblog” buttons appear on everything — but you can no longer reblog a post to the same blog where it was originally posted. I don’t really understand why they’d actively prevent this, since it’s handy in some cases and anyone who abuses it can be easily unfollowed. But Tumblr is Tumblr, and who but mere Users are we.
Back when the solar system was still forming, I wrote a bookmarklet that gave you a universal reblog button, expressly for the purpose of self-reblogging. With these changes, the bookmarklet isn’t useful anymore. You may therefore now gently delete it, dallying for a moment to reflect on simpler days, when the wind blew cool and sweet and the reblogs flowed like summer wine.