The question What does “would not have been possible had I remained” mean? was closed as general reference.
It's a grammar question. Of course any grammar question can be looked up in a grammar textbook — once you know which grammar rule applies. But how was the asker to know which grammar rule would apply? One commenter left a link to a non-authoritative source that can only be found by knowing the answer.
Grammar questions are very different from questions asking for the meaning or construction of a word, where the word to look up is the object of the question. Here, figuring out which entry in the grammar textbook applies is the whole object of the question. The general reference close reason doesn't apply.
And lest someone mention ELL…
- I'm sure that some people will say that since the asker doesn't know something about English, his question must be off-topic here. But this is by no means consensual.
- In any case nobody told the asker to go to ELL.
What could possibly justify saying that this question is not answerable here?