I'm a bit confused about this procedure.
I mean: I know that sometimes one solves the question in the comments, and the comment itself is something that need not be transformed in an answer.
I also understand that seeing an unsolved answer (when it's already solved by comment) may attract some weird and unnecessary answers.
But if the practice is to close those questions, why there is not a specific flag to do so? I.e. "flag->should be closed...->solved by comment". I think it would be best, also for referencing (one has the same problem, searches and finds the yellow band saying that the answer is solved in the comments).