This has been discussed before, but there's no functional way to make it work. Who determines when a question has been answered well? Most of the time, the OP does not have the knowledge necessary to evaluate whether an answer is good or not. Plenty of times, we see answers in this sub that sound good, but are in fact complete nonsense. The mods might be able to do a better job of evaluating whether an answer is functional or not, but that would add a huge burden onto an already overstretched team of volunteers. Also, marking questioned as answered would probably reduce the amount of flairs/knowledgeable users taking a look at the thread.