What to do with the solved questions concerning a mistake not linked to the question?

Question

This question has for aim to help reducing the number of unanswered questions.

Looking to the unanswered questions I went through this question called Error typesetting large bracket with multiple lines. Actually the problem was just that the amsmath package was not loaded, and had nothing to do with the error mentioned in the question.

There wasn't a real conceptual/theoretical TeX-related problem here, so what should be done with this question, and more generally with all the questions presenting the same kind of problem due to something not at all mentioned in the question and not really useful for other users? I would say that knowing that someone forgot to load a package does not improve the general use of TeX and so may not really deserve an answer which will remain on TeX.SX...

What do you think? What do you suggest to do for these questions (I already saw other questions presenting the same problem but I am not able to find them just now)?

Answer 1

Converting my comment and Madam barbara beeton's comment into wiki-answer:

Good to know you are working hard to reduce the number of unanswered Q, Two Options: 1. comment to @egreg to convert his comments to answer ( which has nice explanation of why the error was not "amsmath not found") 2. Directly make an answer from egreg's comments ( I know egreg does not worry too much in doing so). I am pretty sure with egreg's explanatory comment on cases error info, it becomes a deserving an answer even though it's a small missing package issue. Basically adding value for the answer.

quite a few such questions have been closed as "off topic" or "out of scope" (or whatever the currently acceptable reason is). another question (which i haven't tried to find because i'm limited on time) suggested giving a quick answer, to be polite as well as to provide definitive closure, then making a comment giving the reason for closure, and voting for closure. the panel shown when "out of scope" is chosen now provides a space to fill in a custom reason.