Classic Tumblr: the only site fucked enough to let you edit other people’s posts. Try all you want, Twitter, you can’t possibly add a worse feature than that.
You can’t edit the post on someone else’s blog, but you can when reblogging it to your own. This means that anyone who rebloggs the post from you, someone who reblogged from them, or anyone else down the chain will retain your edits. It was really popular to do this to John Green.
Edit: Fixed a mistake.