If the best answers to the question already exist then duplicating them introduces what amounts to update anomaly and diminishes the long term usefulness of both questions by spreading the knowledge between them.

So long as a [question closed as duplicate *isn't* deleted][1] then it still serves to help others find the question with the canonical answers. (Automatic redirects for questions closed as duplicates with no answers might help avoid the "clicking chains of dupes" problem. There's several questions on that already: [Q1][2], [Q2][3] [Q3][4], it seems this was added recently for anonymous users)

That said in this instance I don't think a copy and pasted answer from the other question would work - there's no mention of SSO in the other question, so dupe seems inappropriate as things stand.


  [1]: https://blog.stackoverflow.com/2010/11/dr-strangedupe-or-how-i-learned-to-stop-worrying-and-love-duplication/
  [2]: https://meta.stackexchange.com/questions/29385/close-duplicates-only-when-the-original-was-answered-and-redirect-future-viewer
  [3]: https://meta.stackexchange.com/questions/104284/should-be-closed-as-duplicate-questions-redirect-to-what-they-are-duplicate-of
  [4]: https://meta.stackexchange.com/questions/125220/automatically-redirect-anonymous-user-from-unanswered-duplicate-question-to-corr