In your story they are corpses. In canon, they're green humanoid monsters wearing hooded robes, that represent despair. Considering Rowling's own pro-death position, I don't think it's likely she would have deliberately created enemies that were supposed to be the physical embodiment of death (although the movies showed dementors and death as looking nearly identical). Given the changes I saw you make to them in order to make your point, I assumed it was just something you were changing completely from canon. Apparently I was wrong. Did you think of dementors as representing death while reading Prisoner of Azkaban, or is it an idea you developed later?
In canon, they're green humanoid monsters wearing hooded robes,
Um, what? Description from Prisoner of Azkaban, emphasis mine:
"a hand protruding from the cloak and it was glistening, grayish, slimy-looking, and scabbed, like something dead that had decayed in water; the thing beneath the hood, whatever it was, drew a long, slow, rattling breath, as though it were trying to suck something more than air from its surroundings."
Nowhere does it say that they are green. The best description I can think of is "flying corpses that hide their appearances," which works pretty well as a symbol of Death.
(The HPMOR discussion thread after this one is here.)
The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: