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You can't delete posts because all posts are stored on Steem's blockchain. All you can do is edit your post to say you have deleted the content

This. Its built that way by design. Like the ledger of an accountant, where errors can be corrected, but never be removed.

Thats a shortcoming i would say. Maybe an option to hide a post would be the most welcomed.

Yea that is surely an option; but there should be someway where the blog doesn't appear on your timeline.

You could perhaps open your post and EDIT to either remove all content or just leave an 'Ooops' or 'posted in error' within what is then effectively an empty blog.

Not the most elegant of solutions but it is one way around the problem. Though I'm sure there are others here who can who can give you alternative(s). Good luck with it.