|"Tufenuf ought to get Best Ans but I don't know how."|
Only the person who started the topic can flag a post as Best Answer. which flags the topic as Solved (even if it hasn't been).
Once a post has been flagged as best answer, that can't be undone by the person who started the topic.
You may be still able to click on the up arrowhead on the right side beside the Score box in his post, though, to mark it as a good post.