The book appears to contain useful information for the current catastrophe.
Strange.
Question, if Big Sister's face is frozen in the expression she made when infected then how can she bite you? And how is that a given?
Also by "safe to buck" I ASSUME you mean you can kick her without infecting yourself. There is another use of that phrase some humans may actually find as an invitation to have "relations" with my infected porcelain pony sister.
Hello! to answer your questions, the clay earth ponies can move their jaws but the rest of their face still states the same (I may have misunderstood what an expression is though). Not letting them bite is a given because the individual writing this assumes this will be the first thing everyone finds out about the infected. And yes, "safe to buck" means you won't get infected, not any of that other stuff you're thinking about.