There are already several feature requests related to comments, such as docking comments to an instance, getting notifications or enabling comments for guests, which I would really appreciate and I’d like to add one more 
It would be incredibly helpful to be able to mark comments as “To-Do” after reading them or at least set them back to unread. Often, I review all the comments with my client, and while discussing them, they are automatically marked as read. Some comments can be marked as resolved, while others remain in the prototype as information for developers during implementation. However, when I start making design changes, I have to go through all the comments again to distinguish between “note comments” and real to-dos. Having only “Unread,” “Read,” and “Resolved” states is insufficient for my ideal workflow.
It would already be helpful if I could set comments back to “Unread” after reading. However, a “To-Do” flag would provide a cleaner distinction than simply marking them as unread.