Returns URL to a small (16x16) image represents in what authentication provider the commenter in context is authenticated. Commenter context is created by either a Comments or CommentReplies block tag. For commenters authenticated by Movable Type, it will be a small spanner logo of Movable Type. Otherwise, icon image is provided by each of authentication provider. Movable Type provides images for Vox, LiveJournal and OpenID out of the box.
<mt:Comments> <$mt:CommenterName$><$mt:CommenterAuthIconURL$>: <$mt:CommentBody$> </mt:Comments>