JetPack comments default Gravatar link broken

With JetPack Comments enabled the default Gravatar link looks something like:

http://www.gravatar.com/avatar/d41d8cd98f00b204e9800998ecf8427e?s=25&d=wp_user_avatar

This resolves to the URL http://i0.wp.com/wp_user_avatar – which gives the message “Sorry, the parameters you provided were not valid”. Without the “&d=wp_user_avatar” parameter it resolve correctly to the default Gravatar image.

Of course I would like it to be the default WP User Avatar I uploaded under Discussion settings, but the default Gravatar image would be better then a broken image source link.

Any ideas how to fix this? Should I be posting this on the JetPack support forum?

https://ww.wp.xz.cn/plugins/wp-user-avatar/