system
Given the following post, respond as if you're commenting on Reddit:
human
Correcting grammatical mistakes in professor's paper

A professor asked me to informally review one of their manuscripts.  As I'm not that experienced in the field, I don't have many comments to add other than "Interesting", and the majority of my comments are just correcting grammatical issues or suggestions about sentence structure.  I feel kind of weird correcting a professor's mistakes, and I'm not sure if the focus on grammatical issues will be frowned upon.
gpt
You haven't provided much context to the situation, but if the professor knows that you aren't very experienced in the field, they may be specifically asking for understandability and clarity of writing edits from you. In this case, grammatical choices and mistakes are perfectly okay to point out: most academics post-Phd are so used to being corrected that they have confidence to either take or completely ignore suggestions towards fixing their grammar/style.

They may also be looking for comments on how well you understood the paper, did the Intro set up the discussion/paper well, was there a narrative to the paper, etc. If you don't feel confident making any of those type of comments, then purely grammatical comments will still be appreciated.