There is a number of 'unanswered' questions which are not going to generate any further discussion because they have been answered succinctly in the comments. This is irritating when browsing the list of 'unanswered' questions. What can we do about this?
Would it be possible to implement some feature that lets moderators/users mark a question as 'answered', even if there have been no formal answers (so long as the question has been satisfactorily answered in the comments)? (Or transform a satisfactory comment into an answer, etc.)
The procedure used by the Crusade of answers, which specializes in trying to reduce the unanswered questions queue, is a synthesis of the aforementioned strategies:
Consider if there is a legitimate reason to vote to move/delete/close the question.
If not, ask the commenter using the @ feature to convert his/her comment to an answer.
If there's no response from the author after a day or two, write a CW answer attributed appropriately.
Even though the question has an answer, it will remain in the unanswered queue as long as its solutions have $0$ (or fewer) total votes each. So, one can then visit the Crusade of answers and drop a message requesting readers to evaluate a CW conversion. If it's OK it'll get a vote or more and be resolved!
This was discussed before: see Close/flag questions as answered and the posts linked there... and the posts linked there... Concerning the feature request about marking a question as 'answered': it will not happen. SE considers comments to be transient "napkin notes", not something on par with answers. If a question deserves an answer, there should be an answer posted as such. If it does not deserve one, it should be closed and deleted.
Do no hesitate to rework another user's comment into an answer (with attribution): this is in the spirit of the Creative Commons license under which all content is posted here.