Depend on whether the Prophet was in total control and Sarah was completely suppressed.I cannot buy that the Prophet inhabiting Sarah Sisko's body managed to act like a human being convincingly.
If instead the Prophet was just providing guidance and overall goals, while Sarah was in control of second by second actions, then the Prophet wouldn't have to "act like a Human being."
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I took from it that the Prophet had total control of Sarah because she left Joseph and Benjamin when the Prophet left her body. I think it's a case of the writers not bothering to explain it so I made up my own explanation
) and this would work for me.