In fact, there was a scene here that reminded me of another good movie - Mullholland Drive - that bared and flaunted a specific multiple-interpretation scene to needlessly and abruptly drop a hint rather in the middle of the movie. When you use a scene as a hint dropper and not a narrative driver, you give away the ending. (This is the scene where this aspiring actress meets a cowboy in a boxing ring). The movie was significantly less interesting after that point. That scene was disconnected, random and unreal. The entire movie was like that. But that scene was a little bit more of all that than it needed to be.
In Shutter Island, Scorsese starts by working with a consistent and needless penchant to show too many images flashing through DiCaprio's mind. On top of it he experiments with nested dream sequences that probably work better as a decoy in a novel than in a movie. He might as well put a caption saying "I am going to seed something now". And then finally in a scene where DiCaprio is found alone talking to a severely injured and disfigured mental patient, Scorsese gives away the ending. This movie simply fails to supress too many scenes/events/dialogs and is unable to push it to the background. They just float and strut about winking at the audience.
Therein lies the key to good Noir. Directors who make great movies in this genre resist the urge to use overly clever dialogs during moments that has to both be consistent with the illusion being created but at the same time play the role of a ticking bomb that will explode with multiple interpretations later on. Scorsese has been unable to resist the urge and makes the scene needlessly out of synch with the flow of the movie. After this give-away scene, the movie becomes a little bit of a disappointing journey towards the obvious. The pay load in the end is not a satisfying single moment that reveals everything and connects all the loose ends in a single stroke. The payload comes in several installments, which go about painfully describing 'how it happened' in slow detail. Once again, this movie is for a big part a gripping tale. Definitely recommend a watch. But more was expected from Scorsese (or whoever was responsible for the adapted screenplay).