The same thing happened to me! I believe this label is displayed because your theme is older and might not properly handle the new “post format”.
While I’m sure displaying the “Standard” label isn’t harmful, I didn’t like it. I didn’t feel like updating the theme to support the new post_format, so I eliminated the post_format by connecting to the db and running
delete from wp_term_relationships where term_taxonomy_id=185
Obviously, make sure the term_taxonomy_id for ‘post_format’ is 185 in your db.
