Yesterday I asked this question (Polar-dwelling youth finds an offplanet bride, but she dies, but he adopts exiles as his tribe) and today I found out the answer and answered it myself.
I have found that some of the details in my question were misremembered. I've added a comment with the correction. Should I:
I would say no. Were it not your question, you wouldn't go and "correct" OP's memories of the book, so you shouldn't in your case either. You posted the question as you remembered the book, and that was what you remembered, so the question really can't be "incorrect."
What I've usually seen in any case where the suggested (presumably correct) work disagrees with details of the question is to call out the points of disagreement. If OP accepts that answer then it is a tacit acknowledgement of their mis-recollections, and even then we tend to discourage people from "correcting" their question.
As Valorum notes below, the same details you mis-remembered in your question might also be details that potential future searchers might get wrong too. (Especially if you've conflated the work you're searching for with a sequel, another book by the same author around the same time, a different book with a similar premise, etc.) In that case the "incorrect" question could actually be more useful than one that is strictly correct.
In general, I will not remove anything in a question that will invalidate current answers. If I come to realize later that there are incorrect details, I may apply the strikeout formatting as per this question where someone mentioned a detail matched with another film, and that made me realize that I was remembering two different works. If someone had already posted an answer, that gets a bit more fraught, but I think that the strikeout formatting will still work there, probably with a note indicating why that bit was removed.
As user14111 indicated in their comment, adding discrepancies in the answer is excellent practice. For one, it informs further querents. Second, it provides some honesty that the answer is not perfect (and may not be right). Third, the querent contemplating whether their memory is correct on that non-matching detail can sometimes get them to realize even more about the item they are looking for ("Wait... did the bank manager not run off with the mermaid? But no, I distinctly remember that the closing shots of the film was of family pictures of them and their kid... which is something I don't have in the question").
