Regular users cannot close questions as duplicates if the original question is unanswered (as per Stack Exchange definition of answered, i.e. answered and upvoted). If they try to do so they receive the following message:
This question does not have an upvoted or accepted answer.
I thought of a potential workaround for this. As a user with a gold tag badge I can edit the list of duplicates on a question. When I picked a random question that was already closed as a duplicate I did not receive the above rejection message when I tried to add the question that was unanswered:
I was then able to click "add", again with no problem:
And I was even able to save it with no problem:
And this is documented in the Revision History:
And to complete the workaround I was then able to remove the original duplicate:
And save it:
And this too is documented in the Revision History:
Thus, in just a few steps I was able to subvert the block on regular users closing questions as duplicates of unanswered questions. This seems problematic. If regular users should not be able to close such questions (which I happen to disagree with) then I should not be able to close it just by throwing in a couple of extra steps. And if regular users should be able to close such questions (which I happen to agree with) then they should be able to do it from the outset without having to trick the system.
The above was all done on a test question. However, when I tried to use the same trick on the actual question that I wanted to close (since deleted), it didn't work. Since the question was currently open I had to first close it as a duplicate of a random answered question. That part worked fine. But then when I tried to add the unanswered question to the duplicate list I got the rejection message. (Sorry, no screenshots for this part because I can't recreate it since I can no longer vote to close the question since I already closed and reopened it.)
So the question now is, if this trick worked on the other question why didn't it work for this question? As far as I can tell, the only real difference (other than timing) was that with this question the original duplicate closure was done by me, whereas the other question was originally closed by others. Is that what caused the difference? If it is then I guess it solves the problem of a single user being able to bypass the system. But if it's not then what is the reason?
Note: This is not a bug report. This is a support question asking about how the system currently works.