Scott Patterson reports: Warren Buffett must be in a romantic mood ahead of Valentine’s Day. The Oracle of Omaha’s Berkshire Hathaway bought $250 million of debt from jewelry giant Tiffany Co. The debt sports a yield of 10%, according to Tiffany’s filing with the Securities and Exchange Commission. Half of the notes are redeemable in eight years, the other half is redeemable in 10 years. New York-based Tiffany said it will use the proceeds to refinance existing debt and for general corpora