No peevedness. Just not sure if you knew. I've explained this before. YOU DO NOT ENSURE THAT THE VISION COMES TRUE BY TURNING TO THE DARK SIDE. The simple point is that Force visions are true. They're always true. The Force does not lie. It might speak metaphorically, but it doesn't lie. Anakin's vision didn't become true because he turned. It became true because it was true. It appeared to him and acted as a self-fulfilling prophecy. The Jedi Council got visions of a greater Sith threat before the Mandalorian Wars. They decided to play it safe. Not do anything dark. Hold back and wait for the Sith. By doing so, they drove Revan to rebel and join the Sith, causing the threat they feared. Anyone who tries to prevent a Force vision is doomed because you can't prevent it. You just have to plan to contain whatever the event is as best you can. Anyone who just sits along and goes with the flow after getting a vision, like Luke seeing Mara dead but not saying anything or really doing anything to stop it, still has it come true. Now, Jacen was probing the Force in Betrayal. Not passively receiving a vision. He was actively seeking out guidance from the Force and examining various trees of possibility. As I've just spent a paragraph establishing, the Force does not lie. So if the Force shows him that doing X means Y will not happen, then if he does X, Y will not happen. Period. Unless the authors don't understand what they themselves write, Luke is safe. The only out which has been given is that Lumiya may have been tampering with Jacen's mind and his visions at that moment in time. If so, his probing of the future could be incorrect or twisted. Or he could be misinterpreting what he actually sees. However, by no means can one declare that attempting to prevent an action means it is doomed to come true. That is a thematic device, not a metaphysical requirement.