My question is different from Should there be a policy about 'One-Link-Only-Answers'?
even if you see above question comment Marc has commented "if the link is only to a SE post, it is automatically converted to a comment" .. then why it does not happen in below case.
I am referring to this answer.
This answer just refers another answer on Stack Overflow. I do remember (when I don't know) that when I tried to do same thing, meaning, tried to refer another answer in my answer, the system has said that this should be comment and automatically posted my answer in comments section under the question. And I think that was right too because if we just refer only another answer then it should be rightfully a comment only. In that case, why has this answer been accepted as answer or even got posted as an answer?
But this does not mean I have a problem with answer because the answer seems to be is correct and I have upvoted it as well.