Open the
Add / Edit Standard Comment form.
From the
list on the left hand side of the form click on the code of the comment you
want to edit.
This will automatically load the comment into the right hand side of the form. Now make any changes you want to, to the comment code or comment.
Now click the Save button.
The Save Comment Dialog will ask you to confirm that you want to save the edited comment, click the Yes button to continue.
The Add / Edit Comments form will update to show the edited Comment.