He did raise an eyebrow at ice bears, opened his mouth to speak before internally editing the question and rephrasing it, "By 'ice bears' I assume you are referring to something different than... bears made from ice?" which, though phrased as a question, was really more of a statement.
His expression hardened a bit when she mentioned that he didn't like his brother. It... wasn't really so much that as it was that he didn't like the choices his brother had made in his life. Sirius was supposed to be someone Regulus could look up to, not someone who's mistakes he had to make up for in order to preserve the good name of the House of Black.
"He has made some dismal choices in terms of people he wishes to associate with," Regulus said stiffly. "Turned his back on his family and we responded appropriately. It's... difficult to forget an insult like that." He knew that it was foolish to get into the gritty details on what happened, as he knew that in other societies the side of the table that the House of Black fell on could easily be deemed the wrong side, making Sirius into the hero that he'd always thought himself to be in the story. But it was difficult to brush off a question like that when he wasn't very good at burying the feelings associated with the topic.