Why was this question deleted after it had been "finished"?

Question

This question was recently deleted. The question had positive score, both answers had positive score, and one had been accepted. It had been closed as well (there's a separate question here about the point of closing questions that are "finished").

Anyway there had been no activity for a couple of days, and so with all of the above said: why would it be deleted? What is the point of deleting questions that have finished their entire lifecycle? I understand the motivation behind closing it (not enough context), even though I disagree with it (the question generated two different approaches to the problem, and I thought had a net positive value to the site). But really it's the deletion I cannot understand at all.

Answer 1

Well, I can't see the deleted question but I can pretty much understand the situation after seeing your question and comments. This is not a proper answer but instead a very long comment in which I would just try to answer your quotes. This will be long but I am sure you won't mind :-)

The question had positive score, both answers had positive score, and one had been accepted

First of all, don't start beautifying/judging a question/answer with the number of upvotes/downvotes it has got. Read it and then decide for yourself. There are many rep-farmers and mystery users who up-vote low-quality questions/answers or may down-vote good questions/answers. Many times votes are cast due to personal choices and opinions. So using scores to start your question is not a good idea.

I understand the motivation behind closing it (not enough context)

So you understand that the question is a PSQ and from now I'll assume it is because I can't see the question, but it's quite clear from the comment section.

even though I disagree with it (the question generated two different approaches to the problem, and I thought had a net positive value to the site). But really it's the deletion I cannot understand at all

Now my question is why do you consider the question to be adding positive value to the site when you know that it's a PSQ? Is it because "it's a good problem that is interesting or hard to solve"? Well, that might be a good reason in general but not according to this site's policies. I think that you are quite an experienced user on this site and you already know quite a bit, but I'll mention it again. This site is for everyone one and for any level of mathematics. A good question or a quality question on this site is a question that shows user's motivation to learn through their research work, thoughts and in the best case scenarios, any type of attempts made to solve the question. If the user doesn't show their motivation for their question, it simply means that they are too lazy to work, or they don't want to learn, they just want others to do their homework, and this is not allowed in MSE or probably any SE.

But what's the discouragement? The asker got an answer to their question

The question wasn't meant to be answered at all. The moment you answer a PSQ you should be prepared to get down-voted and possibly deleted. If you can't accept this then I am afraid that you don't understand the policies of this site very well.

It's very possible to answer "homework" questions with hints, and then the site I believe nets a gain of mathematical content.

No, the site doesn't gain any good content irrespective of how good the question is: if the user is not motivated enough to show context. If you still don't understand look at the flagging statement of MSE below:

This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level.

I tend to agree with you that deletion has become too aggressive but I can understand that some folks don't want the site to be a homework mill.

IMO aggressiveness of deletion is actually proper now that is if you compare it with the history of MSE. Previously, there were fewer users and the policies were not enforced aggressively, which was not correct, but then those were the initial stages of the site and users learned and now they (most of them at least) are experienced enough to act according to the site's policies.

I left this site years ago because of how poorly it was managed. Things don't seem to have improved at all.

If by improvement you are referring to the reduction of aggressiveness towards the deletion of poor posts then you are very wrong, this site is not well suited for poor posts at all.

If I spend a lot of effort in producing a high-quality answer, and then another user -- with no context but enough rep -- comes along and deletes it

The answer is simple don't spend your time answering a PSQ, rather, as you have already asked from us, try to improve the PSQ by motivating the author and once the question has quality with the author's motivation, you may very well post your high-quality answer.

I think the answer went on too long but finally, I would like to say that the site's tough/unfair/harsh (if you consider it like that) policies are for a reason. I can give you a few:

1. This is a professional site with countless students, scholars, teachers, professors, Master's candidate, Ph.D. candidates etc. When they are there to invest there precious time and share their knowledge with the asker, why can't the asker be motivated enough to solve their own question? Is that what you want this site to become? Ph.D. teachers solving home-works? You should notices that the services you are getting here for free, you won't find it anywhere even if you pay for it. Hence, please don't take the site for granted. Respect the policies that help maintain discipline and the professionalism. This respect is directly conveyed to everyone who is contributing here.
2. If homework/low-quality/PS questions are allowed this site will be no different from countless other discussion forums, where no one bothers about anything and the askers think that they can use the site however they like for completing their homework like it's their birthright. If it happens, you will lose the dedicated people I have mentioned above in my first point.
3. As I have mentioned before: The motivation to learn. The website is actually teaching you ways to improve your approach. A first timer doesn't know how this website works but if they are keen to solve their question and learn then they will stick around and take constructive criticism from the down-votes, comments, etc. and keep on improving the post.

This is how I learned and I have been here for just more than 2 months. You have been here for 3 years, I hope you understand better than me.

Answer 2

One of the stated goals of Stack Exchange is to create a repository of good, well-asked questions of general interest with correspondingly high quality answers. The goal is not to help individuals with specific problems at a specific moment in time (though if a specific user is helped, all the better), but to create a searchable database of question-answer pairs that are useful to a large number of people.

Part of what makes a question useful for people in the future is context. A copy-pasted question from a textbook is definitely useful for the person asking the question, and likely useful for anyone else who is using that particular textbook. Such a question might be useful for someone studying out of a similar book, and it might have broader appeal, but it seems to me that the general interest in such a question is minimal. As such, a bare-bones question which simply states a problem (which may or may not come from a textbook, and may ore may not be a homework problem) is not likely to be of general interest, and is therefore not appropriate for this site. The question you cite is such a question, hence it is reasonable that it has been closed and deleted.

It is possible that the original asker of that question could improve it. To do so, they would need to provide some context. Where did the problem come from? Why is the problem interesting? Why is it hard? What are the basic terms begin discussed? For that particular problem, it might be useful to know why the asker believes that $\ker(\varphi) = [G,G]$---without that information, an answerer might produce a proof that is essentially identical to a proof that the asker has already read but doesn't understand. Even a description of what the asker has attempted to do can provide a minimal level of context which will help answerers to provide useful answers which get to the heart of the problem.

Regarding upvotes on the question and answer: neither the question nor the answers actually have that many votes, and there are a couple of downvotes, too. My impression of the community's reaction that question is that is kind of "meh". It should also be pointed out that votes are only a proxy for quality, and that there are a lot of reasons that one might vote (either up or down) which have nothing to do with quality (for example, one might upvote a question which one has answered in order to enhance their own reputation; one might upvote a question because it was posted by a friend; or one might upvote a question because they are taking the same class with the same homework problem). If a question has a lot of upvotes or downvotes (say, more than 10 upvotes, or more than 3 downvotes---people downvote much less frequently than they upvote), then we might believe that the vote totals are a good proxy for quality, but two or three upvotes doesn't say very much.

Finally, regarding closure and deletion of questions with answers, I think that quid♦'s answer to another meta question sums things up nicely: we should judge questions on their own merits. If a question is closed and not improved, then it should be deleted. The existence of a good answer is not sufficient to justify keeping a bad question, though the existence of a great answer might be.