Sorting Hat as Major Player In the Wings?

[D.G.]

No: HPFGUIDX 69732

I remember how surprised I was when the Hat, of all things, showed up 
in the Chamber as what appeared to be an active, conscious emissary 
of Dumbledore.  I'd previously considered the Hat to have only one 
function -- to assess the mental/psychic state of students and sort 
them into the appropriate House.  I knew it was a repository of 
Hogwarts history and lore, because it made this clear in its song.  
Nonetheless, I never really considered it a character with "agency," 
so to speak -- an active free will of its own.  It REacted to what it 
deciphered in terms of a student's characteristics, and then made the 
appropriate sorting decision.

Now, we've learned that the Hat can change its tune when it feels the 
need to; we've also learned that it is in possession of something 
approximating emotional/moral "agency," at the very least, in that it 
seems to have been concerned (even frightened?) by the current goings-
on, and thus decided to sound its warning to the students about unity 
and solidarity in the face of evil.

My question:  Who is this Hat, anyway?  Might it not, in fact, be an 
enchanted manifestation of Dumledore's own mind/will?  I wonder if 
there's a closer link between the Hat and Dumbledore's own "agenda," 
so to speak, than a lot of us have previously considered.  If this is 
the case, I wonder if it might show up again, in a crucial moment, as 
Dumbledore's emissary (or sword-carrier)?

Maybe Hogwart's has a [bumble]bee under its bonnet!?!?

D.G. ("JazzmanChgo")