This question already has an answer here:
This one is more of a netiquette question.
Sometimes I stumble on "unanswered" questions that were actually answered - in their comments.
Those questions are shown as unanswered in the statistics.
What should be done?
Flag the question so one moderator can somehow mark it as answered.
Answer the question yourself (as a community wiki answer), mostly by copying the comments.
Nothing. Move along.
I'm talking about questions without activity for weeks or months.
Give diamond-mods the ability to change a comment to an answer; and allow users to flag for this action.