If guest comments is enabled, and the guest don't register, just add is name to the form, the comment is posted with the guest name but with the avatar of the member that is viewing the comment. This means that all members that see that comment will see their avatar on the comment.
I have reported before this bug on easyblog comments system that behaved the same way.
See item 5:
http://stackideas.com/forums/several-problems-with-comments
Regards