With comments enabled within a Collection, a user can have live interaction on the report. By default, commenting is enabled in every Collection.
In a Collection, go to 'Sharing'. Click on 'Comment'.
A pop-up will open up as below. Commenting is enabled by default. To disable commenting, click on the toggle button and set 'OK'.
Disabling comments will not allow even the project owner to comment.
Commenting on a report
To comment on a report, click on 'Open Collection in Viewer'.
Click on a report to select it. By default, the first report is selected.
Write your comment on the right side and 'Post' it.
The posted comments will be visible to all users who have access to the Collection.