There is no need to approach the commenters to add their comments to an answer. Just do it.
Comments are not intended to have long-term value. They are intended to make suggestions for improvements, seek clarification on issues, etc. Ideally, all comments should result in edits to posts (if they are good suggestions or clarifications), and then deleted when the value has been incorporated in to actual posts.
Further, people who choose to provide advice or reviews in comments are choosing to not post them in an answer. If you want to collect, reformat, or extend comments in a new answer, then feel free. Answers (Posts) are 1st-class contributions in Code Review (and Stack Exchange in general), and comments are much lower in standing.
If your answer incorporates the details from a comment, you're welcome (but don't have) to credit the commenter, but I would suggest that you flag the comment and mark it as redundant and no-longer-needed.
Having said the above, sometimes comments are used to get some clarification in a conversational way.... if it seems that there's still an ongoing discussion between the question asker, and someone who may be in the process of writing an answer, then give it some time (perhaps a day is suitable?) for the person to get their answer together before pulling their suggestions in to a new answer of your own.