On the occasion of this question, about losing rep over deletion of this one
Rubbish does not belong on the site. After a question has been marked as unclear, off-topic or too broad, one might consider to delete the question afterwards.
However, specifically if a question was marked as a dupe, we may very well assume that, even if it is a bad one, obviously either the title or the content is clear enough to understand that it is a duplicate of another existing question. Another question we bear on the site. Therefore, the question has some use as a sign post. If not, we should have marked it as unclear.
In such a case, imho, there are various reasons not to delete the question:
- As mentioned, the question or its title might be useful as a sign post to the canonical one.
- The community rules, but at the same time, the community should rule in a consistent way. If we first say the question is a dupe, we cannot say at the same time the question is unclear rubbish. In that case, we shouldn't have marked it as a dupe.
- Not everyone might agree, but; we should at least consider the fact that if a question was answered and not marked as off-topic, someone might lose rep for unjust reasons.
Alltogether, I think we should leave dupes alone, unless we have a very good reason not to.