Marking a question as a duplicate of another one that doesn't have an accepted answer?

Question

I recently tried to help a user to solve an issue by adding a comment with a link to another answer that I wrote a couple of days ago.

This is the question where I wrote the comment (Question A):

Certain Color for Value Range

and the following is the question I linked for solving the issue (Question B):

Classifying slope (flat, slope, steep, very steep) in QGIS?

They are both about the classification of rasters and could be solved with an analogous procedure. While the OP of the Question A confirmed that the provided link offered a solution, the asker of the Question B didn't accept it (but I'm quite sure that my answer offered a valid solution).

In the past, I voted to mark one of the two questions as a duplicate of the other one but, in this case, it is not possible since there isn't an accepted answer on Question B.

Which should be the suggested behavior in this situation? Leaving the comment with the provided link without any further action, writing a similar answer on the new question (i.e. on Question A, this is what I have done), waiting for the approval of one of the two questions and marking the other one as a duplicate, or what else?

I found this similar question on GIS Meta:

Should we close Questions as duplicates of old, unanswered Questions?

but it didn't help me to understand.

Answer 1

Moderators can mark questions as duplicates of Q&As with unaccepted answers. In this situation I would recommend flagging (which you did) for a moderator to mark one as a duplicate of the other.

I think this should probably be done instead of adding an answer to the newer question. Even without it being accepted, you can still get votes on the original, so the new asker can vote for your original answer. This keeps us a bit cleaner, in having a single Q&A and reducing duplication.

Answer 2

From my reading of Meta SE posts like We should be able to close questions as duplicates of any question it seems that you should be able to vote to close as a duplicate as long as it has at least one upvoted (and not necessarily accepted) answer.

Personally, I think anyone with the vote to close privilege should be able to nominate a possible duplicate irrespective of whether it has any answers. Consequently, I have upvoted the question linked in this answer.