I've seen that several times: an answer makes OP want to change the question in a way that would damage the answer. Obviously this should not be done. In fact I think it is better to delete the question altogether than do that. But occasionally I see it done anyway.
So I believe such behavior must be strongly discouraged. Is it written anywhere that it is a bad thing to do?
Related questions: Should I edit this question or make a new question? and Extending questions and answers gradually
Found another related question later: Should I delete my own question if it turns out trivial after a comment?
(I am on the verge of accepting the answer but something still leaves me unsure)