[HPforGrownups] OOP Thestral mistake?

[T.M. Sommers]

No: HPFGUIDX 65625

davidbartmess wrote:
> 
>      In OOP when Hagrid teaches his class about thestrals, we learn
> that "The only people who can see thestrals are people who have seen
> death".  When everyone arrives at Hogwarts at the start of the year,
> we find the carriages that have always pulled the students to the
> castle, are pulled by thestrals, and this year for the first time
> Harry can see them.  Luna Lovegood tells them though, that "I've
> been able to see them ever since my first day here.  They've always
> pulled the carriages."
> 
>      Now supposedly, Harry was able to see them for the first time
> this year because he saw Cedric die last year, at least that's what
> I'm lead to believe, but the problem is that Harry saw death long
> before last year.  Harry was present when LV killed his mom, wasn't
> he?  Do you have to be old enough to remember seeing the person
> die?  Was Harry in the same room when LV killed his mom?  Possible
> mistake by JRK?  What do you think?

"The only people who can see thestrals are people who have seen death"
does not mean the same as "Everyone who has seen death can see
threstrals the instant they see death."  The first sentence states that
seeing death is a necessary condition for seeing threstrals, but it does
not state that seeing death is a sufficient condition for seeing them. 
There is absolutely no inconsistency in the books in this regard.