Overflow's built-in commenting functionality allows you and your project stakeholders to leave written feedback on any share link. Recipients of your share link don't even need to have Overflow installed to be able to leave feedback as reviewers.
There are two ways to enable comments for a share link:
1) Through the Editor, upon creating a new Share from your Overflow diagram.
2) On the Overflow Dashboard, just by clicking on the share link inside the shared / private folder where it has been saved.
Basic commenting mechanics
If comments are enabled, anyone with access to a specific share link can leave and reply to comments. The only requirement for external reviewers is to create a free commenting Overflow account once. Overflow accounts that were created for the sole purpose of commenting are free, do not expire, do not require prior installation of the Overflow desktop app, and are not tied to a paid organization's seats.
When you turn the commenting functionality on, your cursor becomes an “Add comment” cursor. Just click anywhere on the canvas to leave a comment. Comments can contain text (incl. emojis), mentions, URLs, and images.
You can delete your own comments and resolve anyone's comment. Resolved comments are not visible by default. If you need to see them, you’ll need to choose the relevant option from the filters.
Finally, at the top right of your screen you can find the notification icon, which allows you to receive email notifications each time a new comment is left on a project. You can turn that off if you don’t wish to receive emails. Your notification selection only affects the current share link.
Other commenting tips
1) Comments don't get automatically deleted, even if the element where they were left is removed from your diagram. Instead they appear as ghost comments with the title 'Detached Comment - Element no longer exists'
2) Comments don't get lost if you turn the commenting functionality off. They remain inactive until comments are enabled again.
3) Comments are visible while presenting in Prototype mode only if they are left within the borders of your diagram's screens or shapes.