Another problem that is causing flight from sovereign debt is the seniority of the ECB and other institutions in the bailout pecking order. Let’s say the ECB starts buying bonds again. Since they are the senior creditor, they are getting a better deal than the public at any interest rate. Even though my bond may be the same series as one purchased by the ECB, the preference means that it is getting a better deal because it is more likely to be repaid even though we are both paying the same exact risk premium.
Therefore, any sustained bond buying by the ECB will drive the other investors out of the market creating the need for more ECB bond buying. The logical endgame is that the ECB eventually becomes, not the buyer of last resort for sovereign, but the only buyer of sovereign debt.