We recently had a request (as a moderator flag) from the original poster of a question for it to be deleted (Laying out an enumerate environment evenly in two columns with a picture in between). I deleted it, but there is a suggestion that it would be better handled as a duplicate. The particular question has been 'resurrected', but it leaves the general point. Should we, and in particular the moderators, work on the basis that an OP request to delete something should normally be respected?
(This is basically the point made in the post that Rebecca links to in the comments.)
Deleting a question also deletes any answers that have been given to that question. Therefore, once answers have been given, it is no longer just the questioner involved in the content and therefore the answerers should at least be involved in any decision to delete.
If a question or answer has (positive) votes on it, then that is indicative of the fact that others have found them useful and their views could be said to be relevant as well.
Since the licence to publish material on SE is perpetual, the questioner actually has no rights at all to expect material to be deleted if requested. Now that doesn't mean that material cannot be deleted, but that it is for the community to decide whether or not the material is useful enough to stay. In this respect, my view is that moderators exist to expedite matters: if something is posted that clearly does not belong here then they can step in. But if it is a grey area, the moderators should hold back and let the community decide.
(Note that this is the opposite of the role of moderators on many other forums. There, moderators step in to decide what to do in the grey areas.)
To sum up:
- Once a post has significant contributions from more than one person, it ceases to be a matter for them to decide alone.
- There is a due process for deletion by the community and it should be followed. If, as it may be, we (as a community) are not very active at following up on delete-votes, there are ways of bringing things to our attention: on meta and on chat. Short-circuiting this process should be for occasions where it is clear what the community would decide but, for some reason, it is good to act quickly.
Relative to other SE sites that I know of, we're quite slow-moving on community action. I regard this as a good thing. To quote the Golden Rule of the Second Foundation:
Do nothing unless you must, and when you must act - hesitate.
Among some users there seems to be an aversion to having a post that is marked as duplicate. It happens from time to time that after a duplicate is pointed out, the OP deletes (or wants to delete) the question. This seems to be one of these cases (except that since there were already answers the system prevented deletion).
I understand if people are embarrassed about not having done a sufficiently through search before posting, but duplicate questions are generally useful (once someone has spent the time to find a duplicate—please don't take this as encouragement to post duplicates and waste other people's time). Marked duplicates provide a pointer to the other question and thus make the question's visibility in searches higher. They provide additional phrases and keywords for search engines to work with. As such they make popular questions (and duplicates are usually popular as they mean that several people have the same problem) easier to find.
In the present case there were in addition already two answers to the question. Deleting the question would rob the site of these potentially useful contributions.
Therefore I'm generally against deleting duplicates instead of just marking them as such, even when the OP wishes for deletion.
(There are of course other valid reasons for deletion (questions containing something that should not have been posted online, spam, etc.).)