Does comments in code carry any value for SEO? One of SEO tools says comments does carry some value for some SEs. Is their any research done on this?
If you are referring to <!-- comments --> than the answer is no. These comments are flagged by search engine crawlers as "personal webmaster data" and has nothing to do with the on-page content. Simple way to verify this is to use a text browser or a screen reader and view the page as a search engine would, notice how the comments don't show? Thats because it's internal data for the webmaster.
WebCEO used to (may still) like to see it included. I usually leave a piece or two of keyword rich comments just for the sake of "what if".... <!-What have you got to lose?-->