You and your friends can then add or "post" to the discussion at any time by using the "Comment " button. Comments are appended in the order they were made, and each comment is identified by the author's user name and the time and date.
If you are the owner of the Discussion, then you will be able to delete any comment in the Discussion. However, if you are not the owner of the Discussion you will only be able to delete the comments that you personally have authored, even if you have been given Edit Rights.
To delete a comment, follow the steps in the image below: