To delete a comment:
Log into the CMS
Go to "Browse" and then "Sites"
Select the website with the comment that needs to be deleted
Click on the link that reads "Comments"
Locate the comment that you want to delete and check the check-box to the right of that comment.
Scroll down to the bottom of the page and in the drop-down, select "Delete".
Click "Apply" to make the change.
The change should be reflected on the website shortly after making the change.