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, choose the information tab and click on ‘Comment’. You can attach files and docs to your comments.
If you want to notify people via email about your new comment select the users from the list who should receive the email notification.
To delete the comment just press "delete". The comment will be removed and the name of the user that remove it will replace it: