Some questions have been answered completely in comments to those questions. In that case, what should be done, answer the question officially, even if it means repeating everything said in the comments so that people do not think that the question is unanswered, or leave it the way it is and have people open it thinking it is answered, then face this dilemma all over again?
IMO, unanswered questions should definitely be properly answered, even if it is based on other's comments. Comments are just comments, they are no answers.
However, comments are often just comments for a reason; there are no references, only wikipedia citations, or only cites to other questionable sources. If you decide to convert comments into a proper answer, make it an answer, not just a bunch of pooled comments with questionable sources.
Of course, refer to the comment's authors, especially if you have used them as a guidance.
If there are authoritative comments, you can always comment and ping the author to ask for permission to answer using author's info. Or go to chat and sort it out beforehand. I've done that, no worries.
However, compiling an answer via other's comments without acknowledging them appropriately is, IMHO, a no-go.