Currently, the FAQ provides the following guidelines:
Code Review - Stack Exchange is for sharing code from projects you are working on for peer review. You should only ask practical, answerable questions based on actual problems that you face.
As far as I can tell, Project Euler problems are allowed, as well as homework. This is somewhat surprising by the following definitions, as most of these questions pertain to problems that have already been solved, and people want feedback on their solutions (which I think is perfectly acceptable). According to the answer to this question, Code Katas are fine, too. What about code written to understand concepts, or meant as an example in a book?
Would it make sense to reformulate the FAQ to extend to any code that does something useful or provide some useful functions, as opposed to just showing off language features/design patterns/etc.?
This may be a duplicate, although I think it is broader. In particular, if it is not possible/desired to change the FAQ, could some examples of things that are definitely fine, and of things that are questionable, be given?