You can now easily comment on any text paragraph, figure, or table in Authorea. Simply hover the mouse to the right sidebar and click on the comment icon💬 which appears to the right of the document. You can also highlight some text before clicking the comment icon. You can display all existing comments in the document by clicking on the comment button above the title (there is a counter showing you the number of comments). You can select individual comments by clicking on their "yellow" highlight. Try commenting on this article!
Note: after commenting you will receive notifications for each new comment. If you don't want to receive notifications, click on the star icon ☆ above the title to "unfollow" this document's notifications.