Sometimes I find a question that was closed as a duplicate, but it does not have a reference to the source question.
How is this possible?
Link to example (not reproduced after reopened)
Question was reopened after I say this about our CM.
Message in chat with this question was in 13.09 UTC, after that CM reopen it in 13.17, so this does not seem like cache or timing problem with reopening.
Also this revision does not exist, removing something as in linked question.