Mark's lips tighten at identical twin, the little twitch revealing his disapproval of that turn of phrase. After all, twin is inaccurate and identical is hateful; he's worked hard to look different from Miles, dammit. He's differentiating himself from his progenitor one calorie at a time. Still, it passes without comment. Instead, he asks her an abrupt question -

"What do you think of Miles Vorkosigan, then?"