Why not floo instead of thestral to London?

[justcarol67]

No: HPFGUIDX 91679

Hitomi:
Actually, I'm more annoyed that Harry never looked at what Sirius 
gave him after Christmas.  If JKR had had him do so, there never 
would have been a need to go into Umbridge's office, either time.  
He just could have talked to Sirius through the mirrors, Kreacher 
never could have tricked him, and Sirius would probably still be 
alive.  It's always seemed to me to be a strange plot-hole 
oversight. <snip>

Sue:
I have always been troubled by this as well.  When Harry put the 
mirror away, he vowed never to use it and, evidentally, forgot all 
about it.  Why, when he broke it at the end did he throw it back in 
his trunk instead of in the trash?  Where is James's mirror, we know 
he had one.  I have a feeling the mirror (and perhaps all mirrors in 
the series) will reappear and Harry will be very glad he has it.  It 
is, of course, in several pieces now.  The better to share with 
others he needs to keep in touch with.


Carol:
I don't think it's a plot hole. I think it's a deliberate literary
device that JKR is quite fond of, situational irony, where the
expectations of the reader or a character or both are set up and then
thwarted by a very different outcome from the one that's anticipated.
A simple, clear-cut example is setting up Harry and the reader to
think that Snape is after the sorceror's/philosopher's stone and
instead we find Quirrell. 

This situation is much more complex because it involves the irony of
fate (tragic irony) as well. The reader expects Harry to use the
mirror, but he has sworn to himself not even to open the package
because he doesn't want Sirius to leave Grimmauld Place in some rash
and needless attempt to protect Harry from Snape. The fact that Harry
does not open it prevents him from using it to discover that Sirius is
safe in 12 Grimmauld Place and doesn't need rescuing. So By putting
the mirror away *to protect Sirius," he denied himself the opportunity
of finding out that Sirius didn't need saving and so he goes to rescue
Sirius and, in so doing, unwittingly brings about the tragedy he's
trying to prevent (tragic irony or irony of fate, as in "Oedipus Rex").

Then, too late, he discovers the mirror that might have prevented his
terrible blunder. This time his expectation, and maybe the reader's,
is that he'll see Sirius and talk to him, but instead what he finds
(but denies) is confirmation of Sirius's death. I thought it was a
very moving moment and underlined the whole idea of how our choices,
and our mistakes, have unintended and unanticipated consequences. *If
only* he'd at least opened the mirror and known it was there. *If
only* he'd used it to talk to Sirius instead of talking to the
treacherous Kreacher. But with the mirror as well as the journey to
the MoM, he did the wrong thing for the right reason and suffered the
consequences of human error.

None of that makes further use of the mirror impossible. Maybe it will
reappear in other books, but since we've seen that it can't be used to
communicate with a dead man, I don't think it will.

Carol