My own (admittedly somewhat romantic) hypothesis is that Quirrelmort is trying to correct his past mistakes.
Recall the conversation that Dumbledore has with Harry regarding escalation and proportional response. Dumbledore tells Harry that the Light cannot, must not win every battle, because some victories come at too high a price. Harry, on the other hand, believes that the ends justify the means, and that it's all just a matter of thinking up a sufficiently clever solution. Without Dumbledore's intervention, he would've escalated the SPHEW-bully conflict to the point where it engulfs all of Magical Britain, and quite possibly plunges the Wizarding world into a new dark age of terror.
Does that sound familiar at all ?
My guess is that Voldemort, in his original body, was a bit like Harry. He wanted to optimize the Wizarding society, and in order to do so, he had to take over, and in order to make an omelette, you've got to break a few eggs, and there are people opposing you, and before you know it, you're a Dark Lord and people are skinning your opponents alive in your name. The only option was to fake your own death and start anew... which is exactly what Voldemort did.
(The HPMOR discussion thread after this one is here.)
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. There haven't been any chapters recently, but it looks like there are a bunch in the pipeline and the old thread is nearing 700 comments. The latest chapter as of 7th March 2012 is Ch. 77.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes.
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, nine.
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: