We often have multiple people working on multiple-but-tightly-related features in the same file and it makes commenting a real pain. I get emails and Slack notifications about comments on other designers’s pages. If I’m going through my own comments, I see all of theirs sprinkled in.
To avoid it we work out of separate files. We then have to remember to go merge our files together later, since the work ought to live on as one single file once the first version is out.