Accidental Harrycrux : a question

[lunamk03]

No: HPFGUIDX 155208

--- In HPforGrownups at yahoogroups.com, "Mike" <mcrudele78 at ...> wrote:
snip
> Mike again:
> I think we're arguing the same thing from different directions
here.
> We both agree that when LV "transferred some of his own powers" to
> Harry was what signified *marking*. We'll have to agree to disagree
> on the method of transfer. We have one more clue, which immediately
> follows the above quote:
>
> "'Voldemort put a bit of himself in me?' Harry said, thunderstruck.
>
> 'It certainly seems so.'" (CoS p.333, US)
>
> Is a "bit of himself" a piece of his soul or just "some of his own
> powers" through some as yet unknown means? Like I say, we'll have
to
> agree to disagree.
snip

Luna:
I have a question for you guys:
According to Slughorn, in order to create a Horclux, you need to
kill someone and perform some kind of incantation in order to have
your soul split.
According to DD, Voldemort wanted to create his last Horcrux while
killing Harry (note that he intended to do it with Harry's death,
not with James' or Lily's deaths)
We know that when Voldemort casted the killing curse against Harry,
it rebounded (thanks to the protection Lily gave to Harry and that
required her won death in order to be activated), "killing"
Voldemort himself...
Now, how can a Horcrux have been accidentally created if Voldemort
didn't achieve the killing of the victim in the first place, which,
in theory, is the main requirement for the creation of a Horcrux?