The two-way mirror - a cruel useless plot device

[alcuin74]

No: HPFGUIDX 163714

> Carol responds:
> Harry didn't even know it was a mirror. He never opened the package
> until it was too late. His reason: He didn't want Sirius Black to 
come
> out of hiding to defend him against Snape if Snape gave him a hard
> time (the whole reason that Black gave him the mirror). "'Okay,' said
> Harry, stowing the package away in the inside pocket of his jacket,
> but he knew he would never use whatever it was. It wouldn't be he,
> Harry, who lured Sirius from his place of safety" (OoP Am. ed. 523).

Alcuin:

I stand corrected.  You're right.  Nevertheless, I can't understand 
why Harry wouldn't have at least opened the package at first chance to 
find out what it was, even if he didn't intend to use it.  It was from 
*Sirius* after all.  Had he opened it, he would have realized it was 
something he could have used to communicate with no risk of being 
caught.  I also don't understand why Sirius didn't remind Harry of the 
mirror when Harry talked to him through the fire in Umbridge's office.
Surely Sirius couldn't also have forgotten about it.