Task comments allow to you to keep all the discussions and conversations around your tasks all in one place, in context. Every user who has permission to view a given task is also allowed to leave a comment.
To add a new comment, select the task, comments and click on ‘Add Comment’. If you want to notify people via email about your new comment select the users from the list who should receive the email notification.
Note: Currently, comments can be deleted, however they cannot be edited.