Having thought about this for a while now, I have two general comments.
1. It would be nice if, in borderline cases, folk commented to say what they expect. This is particularly useful when the question is closed for lacking context but contains one of: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important (i.e. contains something from the context close reason).
2. We could try and encourage folk to include *more than one of* background and motivation, relevant definitions, source, possible strategie…