Harry to others is, or has grown, jumpy and unhappy with being touched, especially if it is skin-to-skin. Other's pass it off as standoffish, or even haphephobic (fear of being touched). In truth, Harry is post-cognitive, able to see the past of objects or beings he touches.
1) Can be from pre-Hogwarts to post-Hogwarts. Voldemort can be dead as well if it fits the plotline better.
2) Can be accidental or intentional, and can be more expanded than just blaming the Dursleys. Also, it is possible that Harry was born with post-cognitive. 3) Must be someone Harry doesn't trust immediately who finds out, so no Hermione or Ron being the ones who discover the new talent. 4) Harry has problems adjusting to the gift/curse and could react negatively, like pushing away from everyone and becoming intorverted. 5) Can be slash. Yes, I know dear, short, no? If you take this challenge, I'm sure I will add a healthy new amount in the future. It just jumped into my head, and I decided to send it to you before it fled.