BuddyPress.org

What if you removed the existing bp_core_fetch_avatar_filter from get_avatar and then created your own copy that passed ‘no_grav’=>true into the bp_core_fetch_avatar function?

I think this should kill the attempt to use Gravatar to fetch an avatar. I’m assuming that bp_core_fetch_avatar isn’t being called directly anywhere. If you do find anywhere that does, it should probably have a ticket raised against it.