This panel presents a simple list of banned IP addresses along with a link to unban the IP. Because of the methods used by comment spammers (eg using hundreds of compromised PC’s as robot systems) banning IP addresses affords no protection against comment spam.
IP banning is useful only to block comments from a known visitor whose comments you do not want to appear on your site. Even then it is of limited usefulness as a semi knowledgeable person can easily circumvent the block by browsing to your site through a proxie server.