Word that describes a stand in or a frontman? was referred to another question, Word for Powerless Position?, which apparently did not answer the question, as the questioner selected my response as the one they were seeking on their question, an answer not offered for the other question.
What has happened is that the 1st question was closed as a duplicate of the 2nd. The system of closing is what made the link (by the choice of the user who closed it, who, by the design of the system, was allowed to do this as a single person).
To undo this link, you'd have to get the closed question -reopened-, by the usual means.
As to the suitability of reopening, I think you need to make a reasonable case for it. Your justification is a bit hard to follow and what of it that I do follow is not very convincing. Just because a questioner approves an answer doesn't mean it is 'correct' and subsumes all possible answers.
Why would we want to split answers between the same question asked slightly different ways? If someone is looking for a “word for someone who holds a position but they have no real power” they should be able to see all of the answers we have to that question on the site.
Closing a question as a duplicate doesn’t affect your answer or its acceptance by the author, so I’m not sure what you would hope to accomplish by having it reopened. The link would in theory make your answer more visible.