When I peer review, I read their paper once, then I go through again and start to make comments. I comment on anything I have an opinion on- it could be grammar errors, something I think needs clarity, something I think is unnecessary, anything that comes to mind while reading. I tend not to hold back when I’m reviewing because I personally appreciate any comment that someone makes on my paper to help me become a better writer, so I try and do that for my peers in return.
When my peers reviewed my paper, there were many comments left. I overlooked a lot of grammar issues, so I got a lot of comments on that, whether it was a missed comma or a run on sentence. One of my peers also pointed out that some of my sentences seem to stop mid idea so they told me to elaborate on them. After reading through all of the comments I will go through my paper again and I will re-read it, making changes as I go incorporating the changes made from the comments.
I like that you offer comments and suggestions to help your peers improve. As you pointed out, as a writer, those comments can be really useful in helping to develop or polish a draft. Thanks for sharing your process!