If I could route a signal from here-and-now to an event in my past light cone, then clearly I could make an irresolvable causal paradox by having the arriving signal disable the button that sends it, so I'll choose to believe that I can't send messages back in time TO HERE. Now I've heard it said that superluminal messaging would boil down to the same thing, but I don't see how. I can see how it could look to another observer like a message travelling back in time, but not to BACK HERE, and I think that a message arriving in the past OVER THERE is harmless to causality. To get it from over there back to here, still appearing to go back in time, that observer would have to turn around, so it's kinda like the twins paradox. One thing that all observers agree on is the light cones of a given event, so if a travelling message looks spacelike to somebody then it looks spacelike to everybody, and whether it's in the top half or the bottom half of the spacelike zone is immaterial to causality, isn't it? So was I misinformed about superluminal messaging leading to some kind of causality paradox?