Given the power of sovereign debt ratings to rock the world markets, investors might be surprised to learn of the kid-glove treatment accorded to top credit-rating agencies under a raft of new rules proposed by the Securities and Exchange Commission.

You could be forgiven for thinking that, in the wake of a credit crisis spurred by the disastrously flawed U.S. credit-rating industry, credit-rating agencies might have been the subject of drastic structural reforms. You would be wrong.