This question -- SVD for PCA: Why would one standardize the data matrix? -- was closed as a duplicate at 16:59:24 (nine minutes after having been posted). I can swear I saw it closed and without answers (that is when I wrote my comment). But then at 17:00:02 an answer was posted.

Answers cannot be posted to closed questions. So this is clearly due to some glitch or a loophole that allowed posting an answer within very short time after the question closure. I remember discussing a similar case in chat some time ago and one of the mods said that indeed it can happen.

I am curious what exactly the glitch/loophole is, and whether it is a bug or by design.

(Is it that if somebody opened the question page before the Q is closed and so can access the answer form, then they will be able to post an answer? So the SE software does not check if the Q is closed when receiving an A? Or it does check, but intentionally allows some leeway? Or is this leeway an unintentional consequence of some database updates taking time to propagate? Etc.)


There's a grace period after closure where an answer can still be accepted (however the Post Your Answer button becomes disabled, so you have to be clever enough to find a way around that).

In this case the posting of the answer came so close in time after closure that the button was probably still working at that moment.

  • $\begingroup$ Thanks, this answers it. I should have searched on Meta.SE... (Your link also mentions that the Post Your Answer button might never become disabled in a mobile app, so perhaps that is what Kodiologist was using.) $\endgroup$
    – amoeba
    Sep 15 '16 at 20:54
  • $\begingroup$ @amoeba I was using plain old Firefox on a Linux PC. I didn't notice the closure till after I submitted my answer, though. $\endgroup$ Sep 15 '16 at 21:36

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