Source code commenting is essential to the maintainability, readability, and quality of code. Are reviews for such comments on-topic on this site? Alternatively, do we want these types of questions on this site?
These are called "source code comments" for a reason :)
The help center explicitly stated that "any or all facets of the code" are reviewable. The code presented in the question still needs to fulfil the other conditions for being on-topic.
Notably that means it's not on-topic to ask a question that contains only comments, as those don't do anything. I don't see any reason to explicitly exclude comments from review.