<p>I'm not aware of such a policy, and I don't think it exists.  </p>

<p>No upvoted answer (as @amoeba mentions) is a policy that at least would make sense for the SE team to have implemented:  Presumably the close voter could upvote an answer on the target thread if they thought it had sufficient merit.  If they don't think any of the answers are worth an upvote, why should the OP take them as good enough to use to resolve their issue?  If the close voter is the answerer on the target thread, but no one else has ever upvoted it, then it may be good enough, but we might not want to trust them, as they are hardly unbiased.  Etc.  </p>

<p>On the other hand, whether an answer is accepted is not something that most anyone has any control over (except the target thread's OP, of course).  We certainly see plenty of questions that are asked and the OP never shows up again, even when really good answers are provided.  Several times, I've seen a new OP post a thank you comment, but not accept, most likely due to unfamiliarity with how the SE system is designed to work.  Etc.  At any rate, the point is that it wouldn't make sense for the SE team to have implemented that rule.  </p>

<p><strong>tl/dr:</strong>  If you believe a question is well answered elsewhere (and you probably should have already upvoted the answer you think is that good), close away.  As @whuber suggests, if you are blocked from doing so for some reason, but are confident of your choice, flag it.  </p>
