By Luis Arroyo, in Madrid | The Greek restructuring has been a most impressive achievement. But it has fallen only on private investors’ heads. Public bondholders, like the European Central Bank (ECB), refused to take in their share of losses as everyone else did. When the EBC’s governor Mario Draghi was asked about the ECB’s special protection, turning the central bank into a super-privileged investor, he replied: “I can answer…