The question https://scifi.stackexchange.com/questions/42882/why-couldnt-harry-destroy-horcruxes-by-touching-them doesn't have any answer. It is just closed as duplicate (with which I am strongly agree).
To get back my reputation due to downvotes (which isn't appropriate as mobile version of site doesn't display suggestions), I tried to delete it. But, I failed. Why? Previously, I have successfully deleted my own questions.
Based on a few tests done on this very meta post, it appears that I can delete questions that are still open (if they meet all the other criteria for self-deletion), but not if they are closed.