Just a moment ago I came across this question Ubuntu 18.04, complex network configuration with Netplan. OP solved his problem on his own and added that in the question body. However, Thomas Ward added that as an answer in the answer section and made it community wiki (which I appreciate as a I'm not that old contributor and saw that first time) and I edited the question to delete things like Solved and answer in the question body.
So, here's the question which arises in my mind. Sometimes it may happen that OP solves the problem on his own and write that in comment or question body. If I motivate him to write that as an answer in answer section, he might write that. But the problem arises when OP solves problem the same day and writes the solution as an answer. Due to the policy of Stack Exchange he can't accept his answer before 48 hours of posting the question. Also, once the problem is solved some contributors not even bother to at least log in to the site. While on the other hand if some other contributor (like Thomas Ward) write that as an answer and made that as community wiki (to avoid reputation change), OP can accept that answer on the same day. So which one is better since I think questions with accepted answers are far better?
Also, day before yesterday I came across a question (I don't exactly remember) seemed to be an exact duplicate of an existing question. But the problem was that the question had an answer from OP but it was neither upvoted nor accepted. Due to this I wasn't able to flag that question. In that scenario what should be done? Is reverse of this a solution?