What should be done with answers that are off topic for the site but on topic for the (old) question?

Question

I came up with this question due to a first post review to which I didn't really know how to handle exactly.

I had to review an answer to an old question that would (most likely) be off topic with current site standards (asking for library recommendation). After thinking a bit I didn't know how to exactly review the answer, after all it's barely more than a link only answer but when you check the other answers to the question you see that they are the same and voted up.

Since the answer is actually on topic for that question, seeing that it's the same like the other answers on the question and as not to confuse the new poster why his answer was down voted when it's just as good as the others on that question, I decided not to do anything with the answer for now. Instead I flagged the question as off topic so that it'll be closed and can't get more off topic answers.

Is that the right thing to do? Should I also down vote the answer?

Answer 1

Fundamentally we're still a Q&A site: once a question has been asked, while it is not closed, the answers should be on topic to the question, not necessarily the site.

Obviously if there's a way to answer a question so that it is on topic for the site, that is even better -- and may be what the OP was really after, seeing as they chose the site to put the question on.

_{(And IMHO historic questions should be marked as such, but not closed, if possible, because otherwise they can become out-of-date. Of course all existing answers can get stale because of the lock on votes until after they've been updated.)}

Just confirming, I agree with your action. No, don't downvote the answer, if it answers the question (except where it is a link only answer to a question that's not effectively asking for them).