I originally posted a comment to this question which contained a link to a possible duplicate question. I figured the question was more suited to be closed with this duplicate link, so I deleted my comment and then clicked Close and pasted in the same link for the duplicate question. The Possible Duplicate comment was never autogenerated by the system.
I guess the system does that so as not to add too many comments. When voting to close the question though both duplicate options appear and this one has more votes so when the question is eventually closed it's likely it will be closed as a duplicate of that in which case all's well that ends well isn't it?