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A question should stand alone-- its meaning should be clear without checking the tags. One reason for this is that tags tend to be added by other ASE users, much more often than content tends to be added to the body or title of the question by other ASE users. If the relevant content is not included in the question itself, it's difficult to be confident ...
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Personally, I think there is no need to copy information from the tags into the body. The tags are a part of the question. It should be clear for anyone writing an answer what the question is about by reading the tags.
Of course, such information can be included in the body, but I don't think it must be included.
It was noted in a comment here that
tags can ...
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