A tongue that turns into a hand that flips you off — small changes are almost free now.
Riding the Mindaro Line, Katia Grim answered Carl's teasing by sticking her tongue out, then reshaping that tongue into a little hand with a tiny middle finger raised. Carl was startled by how fast she did it. Her own explanation: big changes still hurt, but little stuff like that she can now do with very little effort.
By the end of the run she demonstrated the same control at scale — the Homeward Bound hat she put on vanished into her mass, then reappeared a moment later when she chose to make it visible. Carl's assessment, twice in one chapter, is that she really is getting better at the doppelganger stuff. A lot better.
Flesh rearranging itself on demand, at first painfully and now, for small work, almost casually.
Katia's shapeshifting skill, crossing from grim body-horror utility into something she can use for a joke.