I recall being able to comment in the review queue before. I liked this since it let me leave helpful, personalised comments to guide newer users in the right direction.
However, it seems like it's recently been removed. This seems especially odd, since the guidelines say that you can complete a review by commenting...
This happens in Low Quality Posts too (and presumably others, but the others are all empty for me right now), even though that queue explicitly states "You can also leave a comment on the answer".
Why has commenting been disabled in review queues? And, if there is a good reason for this, can we at least remove the conflicting information?