I'm gonna keep this theory short and simple, because I hate to read long theories that keep saying the same thing over and over again.
I think that the person in the coffin is Sayid. He was probably killed in one of his "missions" for Ben.
That explains why Jack would cry when he reads it. (I can't think of him crying for the death of Locke, Michael, Ben, or whoever you think was on the coffin)
That explains why Kate doesn't care, because she/they think he betrayed them by working for ben.
Forgive my english as it's not my primary language.
Theory by Segle
I think that the person in the coffin is Sayid. He was probably killed in one of his "missions" for Ben.
That explains why Jack would cry when he reads it. (I can't think of him crying for the death of Locke, Michael, Ben, or whoever you think was on the coffin)
That explains why Kate doesn't care, because she/they think he betrayed them by working for ben.
Forgive my english as it's not my primary language.
Theory by Segle
