Users with at least Write permission to an object can go to the Properties: Info tab for the object, and select or clear the Show discussion checkbox. Once a discussion is shown, users with at least RELATE permission on the discussion’s primary parent can add a comment or a reply in that discussion.
To add a comment to a discussion:
Display the discussion by doing one of these actions:
Click the
or 
.Select a single object, and pick View > Discussion.
In the discussion, below the last comment, click add a comment. (If there is no add a comment button for an object, your permission for the parent object is less than RELATE.)
Enter the (required) title, and (optional) body of your comment.
Click OK.
Your comment appears below the last comment, set even with the left margin of the one above it.
To reply to a particular comment:
Next to the title of the comment to which to respond, click
.In the rich-text editing window, fill in the title, and body of your comment.
Your remarks appear below the comment to which you are responding.
If there is no icon for replying to a comment, your permission for the parent object might be insufficient. For adding or replying to comments you need at least RELATE permission.
To edit a comment:
Next to the title of a comment you added, click
.In the rich-text editing window, edit the title and/or body of your comment.
Click OK to put your changes into effect.
Unless you have administrative privileges, you can edit your comments only.