I will occasionally see a question here where I'd like to ask for clarification, expand on the OP's question, or recommend a book or topic for their research. E.g., if someone seems to be grasping for a term, a short answer like "do you mean 'matrilinear societies?'" may point them in the right direction. Are these considered constructive and acceptable, or will they generally be deleted?
Bonus question, on the topic of good responses: if a question has been raised elsewhere (say, on Quora or Stack Exchange), is it helpful to link that discussion here? On the one hand, it seems like that may be better than nothing, but on the other this community does seem to built on the principle "no, 'something' is not automatically better than nothing."
While they can be constructive, if you are posting a request for clarification we expect it to be something necessary to reasonably answer the question. We get a lot of "do you mean X" which are less actually asking for that then they are simply restating the question, or clearly unnecessary for someone actually capable of answering the question.
Which leads to the other important factor, which is that if you are asking for clarification, we would prefer you are doing so because it is necessary for YOU to answer the question.
As for other sites, that would violated the rules regarding link-dropping generally, and Quora/Stack Exchange are generally not the best sources in any case.