Microsoft is working on a new feature for Office.com, their portal for Microsoft 365, which also lets you create and edit your documents in Office Online.
The new feature is called Catch Up and can be found in the app list in the Office.com hamburger menu.
It appears the feature will let you view and respond to comments on your documents from collaborators.
ALumia, who revealed the feature, notes that the comments will be treaded, which should help keep them organized.
It is not known when the new feature will arrive, it seems a pretty useful addition to the Office feature list.