The rule that should exist but does not
The Japanese Language Stack Exchange (JLSE) platform has existed for over a decade now, and while the current set of rules covers the basic guidelines of the Stack Exchange platform, as well as gives users an idea of what types of topics they can ask about, I feel that there's still a very important aspect that is not mentioned anywhere: references to source material.
Questions that lack references to a source
I have only been part of JLSE for a few months, but I have seen many questions that quote some piece of text from various sources without mentioning those sources, but given the importance of context in the Japanese language, I believe that the inclusion of source material should be made more explicit in the rules.
Questions citing textbooks:
Question citing a novel:
These are just a few examples where I asked for the source material to get a better understanding of the context surrounding the question.
Importance of source material
There are a few reasons why including source material is useful, but the most important reason would be to clarify the context of some dialogue or piece of text. You can take a look at the comments on the last question regarding a novel and the comments on Chocolate's answer to that question in order to see how important context is to get a good grasp of what is being conveyed.
However, even for questions regarding purely grammatical concepts such as verb conjugation or particle usage, you will see a lot of questions of the type "Why is X being used instead of Y here?" where context absolutely matters given how many use cases there are for one particle or one verb.
One last reason I want to highlight in favour of including the source material is simply to avoid translation errors or copying errors. Especially when copying text from a physical book, learners are prone to making mistakes (for example in the Source still not provided question). This can have a very big impact on the meaning of a phrase or paragraph, which makes things harder for the people trying to provide answers.
Why context is overlooked
I will gladly speculate about why this rule does not exist yet; on the one hand, advanced Japanese learners and Japanese people themselves are pretty darn good at figuring out the context on the fly and therefore may underestimate the importance of source material because most of the questions on this platform make enough sense to them.
On the other hand, learners of Japanese generally try to ask questions targeting a specific concept or problem that can seem disconnected from the surrounding text. After all, a lot of material in textbooks is taught in chunks that provide the correct context in which it makes sense to use X or Y grammatical construction, word or expression.
The comment section
"All of the issues you've discussed above," you may think, "can simply be solved by asking for clarification in the comments. Is that not what you did?"
Yes, that certainly is an option for active users who care to get the reputation to participate in the platform. But the Stack Exchange platform's philosophy on reputation is very clear: reputation is optional, and therefore the ability to post comments is a luxury, not a basic right for all users.
In fact, if you have a look at the users overview on JLSE, each page shows 36 users and their respective stats. The earliest page that contains a user with less than 50 reputation is page 277. Out of a total of 677 pages, that means that roughly 14,000 users out of roughly 24,000 users simply cannot ask for clarification. That's almost 60% of all users.
While it is entirely understandable that some amount of reputation is required to post comments everywhere, this means that all the users who have less than 50 reputation are left in the dark and have to rely on others to ask for clarification, while most of that clarification could be included in a well-formatted answer that addresses the use case of a certain grammatical concept or word within the context relevant to a question.
When the question askers neglect to provide context for their questions, and question answerers neglect to ask for clarification or context, many answers (while justifiable and correct) might not provide the right nuances for future learners to get a broader understanding of a certain concept they are having trouble with.
This makes learning Japanese from this website especially difficult for intermediate learners, who understand the basics of a language but lack the experience to apply them within different contexts. This context can be figured out more easily if askers are required to provide sources when necessary.