Meta seems to bee filled with questions on this particular subject, and I have seen eloquent and convincing arguments from both sides, but the thing that leaves me ambivalent towards leaving full solutions is the lack of consensus. The majority of the questions related to this topic are on issues of policy, but this question is an issue of "best practices," codified (to the extent possible on MSE) or not.
First let me quote Eric Naslund's answer to this thread, which proposes a policy that opposes full solutions:
I am opposed to such a policy, as I believe it would have a negative long-term impact on the site as a whole.
Here are just a handful of the many problem associated with such a policy:
One purpose of stack exchange sites is to have long lasting questions and answers, this is why we close as duplicates, because the original is meant to be found on search engines, and be a reference for future question askers. Having an inordinate number of questions with only incomplete hint-answers, and where posting a complete answer is not allowed, nearly defeats this purpose. I am not saying hints are bad, they have their place, but having a policy which only allows hints on a whole class of questions is ludicrous. I can imagine situations where people make accusations about what is and what is not homework, re tag questions, and refuse to give full answers. In the worse case, things may degrade into a witch hunt scaring away new users. How much of a hint is too much? What may be a complete solution for one user would not suffice for another. How can we standardize this? It seems to just create a whole host of reasons based on ones opinion of "what is a sufficient hint" to downvote/not vote up otherwise good answers. There are a plethora of ways for students to get help on their homework, and different standards exist around the world for what is and is not allowed. Who is to say your standard is the correct one? I don't think that we should compromise the functionality of the website, the happiness of our answer writers, and the health of the community to try and be some kind of academic police. Hints can be very helpful for students learning, but there is nothing wrong with posting a complete solution.
I can definitely see that line of reasoning, and considering the utility and ubiquity of search engines, I think that full solutions help form a de-facto searchable archive that is much more useful than a bank of hints. If this is combined with the continuing closure of duplicate questions, then one could easily see the residual benefit to the overall community (which is what makes MSE what it is).
However, with this community of mixed ideologies, the inevitability of encountering the idea of the community serving as providing pedagogy must be considered. The argument that full solutions can often be pedagogically harmful to students because of their lack of providing the student with the ability or opportunity to reason through the problem with hints only is also understood.
Personally, I can see reasonable arguments for both sides of this debate, and as both an answerer on MSE and a student I have tried to occupy a middle ground, by avoiding solutions ala Gauss (to use his own words, `no self-respecting architect leaves the scaffolding in place after completing the building') and providing full solutions with the full reasoning behind them, as well as any caveats, special cases, or notational issues that might be relevant. My pedagogical goal (if a high school student may have one) is to allow the person who reads my answer (not particularly the OP) to understand how to reason mathematically in a way that would allow them to tackle problems like the one posted and derivatives (no pun intended) if they were to come across them. This however still contradicts the "hints only" approach to MSE, which (along with the discord in meta) has lead me to asking this question.
I just saw the responses to this question, and I simply thought it might be relevant as an example where giving a hint was pedagogically advantageous.