Leave "Hints" as an answer
I think we can agree that homework questions should not be answered outright. Doing so would ultimately be a disservice to the student, and unfair to his peers. As mentioned in the linked discussion, there's also the concern that people will likely be depending on the student's ability for their security in the future.
Homework questions should therefore be understood as asking for clarification or guidance, and not a solution (regardless of the student's intention!). So I'd argue that hints are the correct type of answer.
I think the hints-as-answers is also preferable to the hints-as-comments proposal. Hints-as-answers allows the best answers to rise to the top, be accepted, etc. It also has the side benefit of signalling that outright solutions are not acceptable, whereas relegating hints to comments seems likely to do the opposite.
How do you vote on an answer that does not answer the question?
The consensus regarding homework questions was that questions that are clearly from an assignment should only be answered in the first place if they include evidence that the student has at least tried to figure it out. So I'd suggest:
- Does the answer address any underlying misconceptions evident in the student's attempt?
- If the student's attempt is on the wrong track, does the answer point the student towards, e.g., a counter example?
- If the attempt is on the right track, does the answer point to an appropriate proof technique, e.g., a reduction?
If the student has provided examples of things they've tried but are now just at a loss of what to do next, then I don't see an alternative to evaluating answers on a case-by-case basis as to how well they point the studentin the right direction without giving an explicit solution.
If an answer provides the solution outright, people should leave or upvote a comment informing whoever left the answer of the site's policy. (Would it be appropriate to flag such answers for moderation?)
What if someone later has the same problem but it is not homework?
This is a tricky issue, because we don't want a student to just claim something isn't homework. I'd say that the best way to handle it would be to use your best judgment with respect to their honesty, but err on the side of believing them and providing an answer. Alternatively, the answer could be complete enough to provide an accurate intution/understanding of the issues without being, e.g., a formal proof that a professor would accept with full marks.
I understand that this approach is not without it's problems, not the least of which is that answers will be more subjective than usual. I do think, though, that it is better than the alternatives.