talking in order to stay sealed
Day is scanning the room for somebody else to engage and piss off so he can prove to himself he doesn't fit in here and stay separated off isolated inside himself
Context
Day's compulsive talk is aimed at no one; it is a tool for staying apart, a way to provoke enough friction that he can confirm he does not belong and blame the isolation on the room. The head is the sealed command post where the disease feeds, and every clever word is deployed to keep the walls up rather than to reach across them, conversation running in reverse, its whole purpose to guarantee that nothing gets in.