As long as we aren't fixing stuff and sending the file back, where no-one but the OP can learn from the experience.
Use our best judgement. If we think we can help the OP faster by getting them to send a portion of the file or a new file with the same problem, why deny ourselves that facility? It can be counter productive to keep asking questions or to speculate, cut out the middle man.
it's like debugging code
It can be very instructive to the original poster to try to reduce the issue to the smallest possible
.blend, sometimes simply getting them to remove all the other possible variables will prove a solution in itself. Just like asking someone to debug their own code by scraping away things that have nothing to do with the problem.
It is important to do a short write up after solving the issue with the
.blend so that the knowledge is text searchable and not dependant on the .blend still being available.
Ultimately the file itself is irrelevant, but an accurate problem description and resolution clarification is.