Anonymous user do not want to show their name and other detail.before publishing comment blogger may ask for security check.
But when if some one comment using google account then image on google plus profile will be shown and if that user have blogger account then blogger icon appear in picture.
How to remove/change default avatar in blogger comment
First you have to login to your account
now go to template and edit HTML
press CTRL+F inside code area then a search box appear
Search for