Thanks carstenback.
Some clarification please:
I had the same problem and solved it by adding the class=”avatar” to the <img> tag generated by the plugin.
Did you add the avatar class, or did you replace the photo class with avatar?
I ask because I wonder what side effects changing the class from photo to avatar has on other uses of the avatar; for example, in author pages.
Additionally,
It would be nice to be able to completely bypass and avoid gravatar use and outbound calls/tracking to Gravatar. The options to bypass Gravatar depend on the global WP Gravatar fallback options enabled. I noticed some code that has been commented out that may manage that.
In summary, I am going to pursue a solution to providing a default avatar in the case the user does not have a specific avatar uploaded/selected, aside from calling Gravatar for one.