Is there a policy for this? Based on my limited understanding of the SE system, I see several options:
- Vote to close the question on money.SE and simply ignore it from there.
- Flag the question for moderator attention and have it deleted from this site.
- Copy the answer from quant.SE to an answer on money.SE. I would make my answer community wiki (I don't get reputation for it then, I think). I would copy the text of the answer from quant.SE verbatim, with a citation to the poster's comment and the quant.SE answer.
For the sake of preventing link rot, I would prefer #3, even though option does somewhat duplicate content between sites. I think it makes it easier for someone stumbling across the question on money.SE to see the proper answer, without necessarily following the comment thread. Although this comment "thread" is only one comment long, I'm wondering about this in general.