Every now and then, we get a question like this one:
As you are aware, lots of recipes call for apples, applesauce, bananas but I am severely allergic to them. Do any of you know of alternatives for these healthy alternatives?
In my view, it is simply unanswerable. It seems to stem from a wrong idea of how cooking works, in that it expects to find a perfect substitute for an ingredient X which behaves and tastes like X under all circumstances and so can be dropped into place without further thought.
But the real world is more complex than that, so frequently there is no answer at all to this type of question. Changing an ingredient both adds taste and changes the structure of the final product of a recipe. A substitution which is equivalent in taste frequently does not exist, due to the complexity of taste, although there are special cases where the difference is so slight that the eaters won't notice. And it depends on the recipe whether the structure/texture of the finished product will work.
As a result, these questions tend to float around unanswered, or to collect random suggestions of the sort "if you are making a fruit salad, any other fruit will do" or "make zucchini bread instead of banana bread".
There are examples of sites on the network which close questions with too little context, and it makes for much more sensible answering. For example, the TeX site requires questions to come with a MWE (minimal working example). We don't need this for each question, but for substitutions, I propose the following rule:
1. If the question mentions no use case at all ("What is a substitution for bananas?"), it gets closed as "too broad"
2. If the question mentions a use case but not a recipe ("What to use as a substitution for bananas in a banana bread?") it can generally stay open. If users feel it's not clear enough, they should use close votes.
3. If the question lists the exact recipe: that's the best case.
What are your thoughts and ideas on getting this rule in place?