Why was my recent answer deleted, and was it really an appropriate action?

Question

I recently asked and answered a question on the main site: What are the Energy eigenstates for a modified quantum harmonic oscillator?

First of all, this question ended up being re-tagged as homework, which I understand. While the question is not the sort of question addressed in even relatively advanced quantum mechanics books, it has a straightforward answer that requires a straightforward conceptual and mathematical explanation that could be addressed in a quantum mechanics class (although, in my experience, it absolutely never is). While I think that labeling this as homework is unhelpful (because it groups this question in with tutoring-style questions - the bane of this StackExchange) and unfair (since a lot of people who I think might appreciate the answer block the homework tag), I understand why it was done.

However, this question has a clear conceptual question built on an obvious hole the curriculum of standard physics textbooks: How can the series solution only converge if the series terminates? The answer, as I explain, is that that statement is simply misleading, and the actual solution goes entirely unaddressed in standard references.

I stated a clear conceptual question in my original post, and I then give a clear and complete solution to the conundrum in my answer.

So I am confused about two things:

(1) Why was my answer deleted? Is this a new standard that off-topic questions have their answers deleted? That seems wasteful and unhelpful.

(2) Why was my question marked as off-topic? I stated a clear conceptual question (i.e. how can a series solution converge without terminating if the references say that it doesn't), and I showed plenty of effort considering the detailed answer that I gave.

This seems like a perfectly legitimate Q&A-style question being unjustly swept into the homework trash heap. It seems clear to me that this question and answer is well-outside what the homework tag is meant to protect against, and I think its worth re-considering if this action against my question was genuinely justified or appropriate.

Answer 1

Our homework policy is mostly about asking homework-like questions, but there is a policy for how to answer them as well near the end of it:

Why don't you provide a complete answer to homework questions?

This is pretty well covered by a discussion on the Math Stack Exchange site.

Providing an answer that doesn't help a student learn is not in the student's own best interest, and if a solution complete enough to be copied verbatim and handed in is given immediately, it will encourage more people to use the site as a free homework service. In the spirit of creating a lasting resource of mathematical knowledge, you may come back after a suitable amount of time and edit your response to include a more complete answer. Or even better, the student can post his own correct answer!

If someone posts an answer to a homework-type question that gives away a complete or near-complete solution, in most cases it will be temporarily deleted.

The temporary deletion is just what it says -- we will delete complete or near complete answers to homework-like questions, and at some point we will restore the answer. We usually wait awhile so that whatever homework assignment prompted the question is turned in and whatever improper utility that can be gained has passed.

Your question is a bit of an edge-case -- your answer did provide a complete/near-complete answer and was temporarily deleted. A comment was left on the answer to that effect. But, well, since you answered your own question then temporarily deleting it doesn't really have the same impact. For starters, you already know the answer! And two, you can still see your deleted posts, and so it doesn't do anything to prevent you from using the information in it right now.

So what happened here is that our usual policy of temporarily deleting answers to a homework-like question was applied -- the answer was deleted temporarily, and a comment was left to that effect. When it was deleted, we didn't realize it was a self-answered question. That's a good sign that we are evaluating posts on their own and not looking at who is involved in asking and answering. It's pretty infrequent that a homework-like question is self-answered right away. Usually a self-answer comes much later when the person asking has worked it out on their own.

I have un-deleted the answer. But if others provide(d) full answers, those would still be temporarily deleted in accordance with the policy.

As for your second question about why this was closed as homework -- that is something I cannot answer. But there is a process to reopen questions. If you edit the question, it will put it into a review queue for being reopened. If your edits make it so that it is clearly not homework-like, then the system should work and it can be reopened. The other way to draw attention to it is by posting here, like you have done. There is already 1 reopen vote, and so give it some time for the reopen system to work.