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I am of the opinion that too many questions are being deleted, particularly those that are duplicates. It seems some people don't even blink when deleting a question with 10 or 20 answers, some of them very good, just because there's an exact duplicate.
I believe Jeff has previously stated the duplicates can be useful for providing more pathways to the answer. Sometimes people ask the same question in a sufficiently different way that the original isn't found so that link is created.
That somewhat contradicts the view that closed questions are one step away from being deleted. I'm not sure if this is the official stance or it has just come about.
I figure we can clarify this by requiring a delete reason. Unless a duplicate has no real answers whatsoever it should pretty much be left alone (imho). There's no harm in it being there and perhaps we can get some clarification on when are the right times to delete.
Edit: Ok, example was requested. Here's one: Why did a question get deleted?. The timeline was:
Someone posted Are regular expressions over-hyped? (now merged so original is gone). But the text was:
I'm a member on several forums that have a subforum dedicated to programming questions.
It is an observation that to almost every single question about finding data in strings, the most common answer is "use regular expressions". And if you're lucky, a link to a tutorial.
For many situations that people will generally recommend regular expression, it's pure overkill.
Many things can be done with substring() and split() functions, yet people always seem to put regular expressions on a throne. Why is this? Does this have something to do with the history of regular expressions versus these OO-language functions? Are the people who recommend regular expressions old farts?
Why in the name of the Matrix should I use a regular expression and test it, to see if a string contains a question mark, if I can just do string1.contains("?");
While in some cases, such as form validation, regular expressions are useful, I find that in most cases I don't need them.
So how often do you use regular expressions, not because it's useful, but because it's what you're used to using.
EDIT: if you're gonna vote to close this, at least have the decency to make a comment as to why!
So until (iirc) Marc intervened, 13 answers had been unceremoniously deleted for something that would've taken one of those offended by the question two minutes to fix. It's that cavalier attitude with deleting content and those taking personal satisfaction in it that I'm hoping to temper (shog9: "I don't regret the outcome. Indeed, it ended far better than i could have hoped for").
Lastly, it's worth noting that labels are important. For example, one close reason we have is "subjective and argumentative". Some view anything subjective as bad and vote to close it. Most of programming is subjective. Even "how do I code X?" can have several answers of relative and debatable advantages and disadvantages. Argumentative (eg trolling) is something else entirely.
The point of all this is that those reasons affect what people do (as most are trying to do the right thing so if they see "subjective and argumentative" they're just doing what they think they should be doing) so having explicit delete reasons should result in a better outcome: the right questions being deleted and less of the wrong ones being deleted.