I think that was a great explanation Carola 9146. I do not believe Voldemort became a Horcrux for Harry. I believe that what Voldemort killed was that part of him that was Voldemort's soul. Because he willingly went to his death for love, just as his mother did, then Voldemort did not harm Harry's soul, he destroyed his own horcrux, that was the scar. I know that Dumbledore knew this when he tells Snape that Harry is a horcrux and must die. I know he knew Harry would not die, but Voldemort would destroy his own horcrux. Had Snape forced Harry to come to Voldemort it would not have worked out the same. Harry had to enter into his own death willingly and for love for that curse to not harm him. Just as his own mother had done for him 16 years earlier. In the end, love destroyed Voldemort, the one power that Harry had and that he would never understand or have.

The Hallows are completely important. As Harry already possesed one of the Hallows, and that Voldemort did not even recognize one, that you know he would never be master of any of them. Harry was destined to be master of them all in the end, and by being master of them all, and destroying the horcruxes, he destroys Voldemort.

As I said, very good explanation given by Carola 9146