Same thing as with http://danbooru.me/post/show/557134/ Please, when you upload pictures, press the "find similar" button to see if that picture is already posted on danbooru, and if it is, dont upload it again if its totally same picture. Like this one, only the file size is different, other than that, its the same picture.
While I agree completely, I'm left wondering about the utility and consistency of the duplicate tag versus parent posts. Looks like there's plenty of forum topics on it, so I'll take my confusion there. ;)