[HannaW]

Hello,
I had just the same question and found a really simple css solution. I haven’t tried it in all browsers though:

body:not(.logged-in) .shortcode-author-avatars .author-list.grimlock-author-avatars__author-list .grimlock-author-avatars__user span.avatar img.avatar {
	-webkit-filter: blur(10px); 
/* Safari 6.0 - 9.0 */
  filter: blur(10px);
	
}

Hope that works out for you!