Stack Exchange encourages the editing of answers for improvement. This carries the corollary that Stack Exchange recognises that answers may be initially offered in a form that is less than ideal. However, as with some other high-traffic SE communities, the ELU community tends to penalise unsubstantiated answers. Note also that one person's fully-substantiated answer can be another's sketch-of-an-answer.
As an aside - if you consider a comment to be a good answer, conveying your appreciation of their comment is often enough to prompt a proper answer.
For the OP, answer location (comment-answer or answer-answer) is often secondary to having their question answered in a reasonable manner. For simple answers to simple questions, leaving them as comments is fine. There is always the risk, however, that comments may be removed without prior notice. To simply preserve comments, copy them into wiki-answers.
For the database, and for more substantial community involvement with answers, answer-answers are preferable. Feel free to post answers even if your answers are based on existing comments. When you do, common courtesy suggests that you provide proper attribution. It should go without saying that your answer-answer should have a sufficiently-high standard of substantiation, particularly when compared with the corresponding comment-answer.