Is it considered a divorce pronouncement, or does it require expiation for a broken oath by feeding ten needy people, after the husband told his wife, "You remain divorced," with no intention of divorce, following his oath to divorce her if her voice rose, and then her voice did rise?

The majority of scholars are of the opinion that swearing by divorce results in divorce upon breaking the oath. This is the fatwa we adhere to. So, if the wife does what she was sworn against doing, her divorce takes effect. If the divorce is not the third and final one, he can take her back during her 'iddah (waiting period).

However, Sheikh al-Islam Ibn Taymiyyah holds the view that swearing by divorce, when the intention is not to effect a divorce but rather to threaten or emphasize, is treated like an oath by Allah. Upon breaking such an oath, an expiation for an oath is due, and no divorce takes place.

Your statement, "She remained divorced," does not effect a divorce, because you thought a divorce had occurred when it had not.