Two review queues, First Answers and First Questions (unlocked at 500 reputation), have an option to share feedback attributed to "Community" on the post. These queues may not have very many posts in them because it only takes one person to finish the review. For this reason especially, you need to make sure you're choosing the right options when reviewing — "Share Feedback" isn't a substitute for a downvote or a flag or a close vote! It just leaves a comment and removes the post from the queue.
(The queues Late Answers and Low Quality Posts also leave comments, but not by "Community".)
From the announcement (note: as a non-code site we don't have all these choices):
If you're not doing a review, you can leave specific feedback using comments yourself. To make this easier, there are some AutoReviewComments userscripts that were developed by other members of the Stack Exchange community. Still, try to leave customized comments where you can; it is not very obvious how someone can add "citations or documentation" for something they intuitively know just from speaking the language, for example.