So, its not ok for two fully health tested merles to be bred but its ok for Jim and Bob down the street to breed their untested dogs? What if Jim and Bob don't know that both of their dogs have a thyroid problem? Still ok? I mean really.
FWIW There were some influential workingAussies that resulted from merle x merle breedings.
FWIW I'm not saying I think it's a great idea to breed merle to merle in Collies or Shelties or breeds at a high risk for blind/deaf double merles. But this sort of thing has been done throughout the history of the breed and the only reason it's being discussed now by people who have no involvement or interest in the breed is due to an article written by someone who seems to think breeding any merle or any Collie for that matter is questionable ethics.