.. Im not even sure what your linearly talking about anymore compared to what started this conversation... You said lash said outsiders cannot mentally whammy him, I pointed out this is untrue. What did or didn't happen on the boat is ilrelavent to that. He's not immune to psychic attack and nobody has ever said he was, not even from outsiders.
Lash said, that Harry has power over Outsiders. You said it was untrue, go reread White Night.. Well, Vittorio possessed/assisted by an Outsider did it. My retort is, he was able because Harry didn't know he could fight it. He was aware that the whammy was on him though, which is a huge step forward in not unknowingly being possessed by anything unless you want to be.
You said that is why Lash sacrificed herself to save Harry from the whammy...True, but also when she did it Harry still wasn't sure how to do it,she had just told him...
My point about what happened with Justine on the Water Beetle, was if they wanted possess Harry mentally or be able to do it, that was the time. Since Harry was exhausted physically, mentally, emotionally, hurting both physically and emotionally, instead Harry figured it out and called the Outsider/Nemeses/Walker out. That is how it is relevant, if we are talking about Harry unknowingly being taken over and controlled by HeWhoWalksBehind. If it was going to happen, that would have been the time, I really doubt that Nemeses would ever find Harry that vulnerable again.
Actually in Peace Talks Harry discovered that he can turn the tables on the Outsiders. When he and Eb were fighting the cornerhounds, they were trying to put the mental whammy on them. Instead, Harry found himself in their head, felt their fear of him, and saw the image of himself that they see.