How to review comment-as-an-answer in Low Quality queue when, and only when the answerer states "I can't comment on the answer given" or similar? (Update: this answer, which very well may have been helpful to the OP, has been deleted.)
Since the answerer is already aware it should be a comment, the deletion comment template --
“This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post.”
-- doesn't help, and makes reviewers sound ignorant.