A lot of characteristics of Harry's were passed to him via Voldemort:
- telepathic connection to voldemort
- the iconic scar
These were caused by a portion of Voldemort latching onto Harry when he was destroyed by Lilly's protection spell.
But a lot of the characteristics that they share in common may have more to do with environmental conditions, such as both being orphans and both matriculating into the magical community at 10-11. They both are:
- resourceful and determined
- strong-willed and motivated
- fascinated by different types of magic
- erudite and intellectually curious
As Tom Riddle puts it,
Voldemort: There are strange likenesses between us. Even you must have noticed. Both half-bloods, orphans, raised by Muggles. Probably the only two Parselmouths to come to Hogwarts since the great Slytherin himself. We even look something alike.
However, Dumbledore concludes that their differences were more important in how they shaped Harry into the person he decided to become:
Dumbledore: Listen to me, Harry. You happen to have many qualities Salazar Slytherin prized in his hand-picked students. His own very rare gift, Parseltongue, resourcefulness, determination, a certain disregard for the rules. Yet it is our choices, Harry, that show what we truly are, far more than our abilities.
So my question is whether or not Voldemort's ingrained horcrux impacted the degree of difficulty for Olivander to pair him with a wand, or for the Sorting Hat to sort him into his house. At the time, Harry had not yet made crucial decisions to distinguish himself from Voldemort; he was only 10 (or close). Regardless, both processes took quite some time compared to other students, though it also took awhile for the hat to sort Neville Longbottom and others. By the Sorting Hat's estimation,
Sorting Hat: Hmm difficult. Very difficult... Plenty of courage, I see. Not a bad mind, either. There's talent, oh yes. And a thirst to prove yourself. But where to put you? Not Slytherin, eh? You could be great, you know.
Did the horcrux "blur" or "cloud" the "right" choice from the Sorting Hat at all? Has JKR discussed this during any interviews or other PR?
Ollivander: Curious. Very curious... It so happens that the phoenix whose tailfeather resides in your wand gave another feather – just one other. It is curious that you should be destined for this wand when its brother gave you that scar.
Would Harry have been (probably) paired with a different wand if it weren't for the Horcrux? Did the Horcrux have an influence on choosing this "sister" wand to such a large extent, that it was one of the only possible outcomes, and thus a more laborious task for Ollivander to determine the proper one?