Someone has recently been flagging lots of very old questions for closure as "primarily opinion-based" or "off topic". In my opinion, there is no good reason to close very old questions, especially if they have many upvotes, or answers with many upvotes, so I have voted against almost all of these flags. But perhaps this should be discussed.
First, let me stress that I am not trying to suggest any specific course of action here, just argue why those flags make some sense. The whole point of this answer is trying to explain a phenomenon, not defend it. Take me as a devil's advocate if you will. I don't have a strong opinion on whether such questions merit closure, and in most cases I personally prefer to keep those old questions open.
If there are old questions which, if asked now, would be off-topic, it does make some sense to close them. The scope of the site has evolved — especially in connection to other SE sites like Mathematics and Academia — and closing old questions that would be better at those sites sends a signal to current and new users. If we want to discourage users from posting new questions of some kind, it can be (in part) signaled by marking old questions of that kind as off-topic.
If a question is months or years old, it typically has received all the answers it will ever get, and closure does not effect visibility or voting. Therefore, while closure might not gain much, it certainly doesn't hurt much, either. Having questions closed doesn't cost any reputation; it only hurts one's question score which isn't all that relevant in most cases.
Moderators can also lock a question and this is one of the offered reasons:
This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here. This question and its answers are frozen and cannot be changed. More info: help center.
Locking makes it impossible to comment or vote, but the question is still visible. I think closing does less harm, but locking is a relevant option too.
I'm not advocating that we should go and close all (or any) old questions that don't fit the current scope. I'm just saying that it's not utterly nonsensical to close at least some of such questions. I assume that sending clear signals and having a consistent scope is what the flags were trying to achieve. But I'm not the flagger in question, so I can only guess.
I am strongly against of closing old question, just because they are old. Imagine questions asked by David Hilbert or Friedrich Gauss. Why would you close them ? There is saying "no such thing as a bad question" in many languages. I have looked "highly upvoted closed questions" link offered by Martin Sleziak. There are many interesting questions with answers. Unfortunately I have no time to read them. Either concerning mathematical career, publishing process or mathematics itself. All of them are valid. We are human beings, so we ask questions and we look for the answers.
Few comments about MO
MO portal is organized as "questions and answers" forum. I am not sure whether it works in a good way. It is not possible to avoid discussions between people on certain subjects. Therefore - even moderators try hard - there are and there will be discussions on MO.
I have one suggestion - to remove down-votes and keep only up-votes in MO policy. No one is happy receiving down votes. This is psychology. What positive do we achieve by putting down votes on someone answer or question?
It is funny, because I received down-vote after I added suggestion to remove down-votes :)
Few comments about closing questions
What is the reason for closing question on MO? The standard explanation says that the reason is "not research level" question. My experience is that sometimes the reasons are:
- person asking is not known
- language of the question is not good - not using mathematical slang currently used
- the subject is not hot topic - currently not on the agenda of working mathematicians, not popular enough to attach interest
For example philosophical questions asked by known mathematicians are accepted. The same questions asked by layman are rejected. Say that I ask "how to imagine 3-manifold ?". That question would be closed as "not research level question". If the same question would be asked by Michael Freedman, then it will be accepted.
There are two questions on this forum with divagations what Sir Atiyah thinks about octonions. This appears interesting and no one dares to close such a question. When I ask about octonions, my questions are being closed. I have to fight to defend my questions against closure. Is it fair?
I agree that questions of type "can someone help me to do homework?" should be removed or moved to stack exchange.