As per a comment by Pavitra in an earlier thread, I think it might be that he's a copy of Voldemort, without (most of?) Voldie's memories - hence the single soul under the hat, the red remembrall, and various insinuations by Quirrelmort.
In the latest couple chapters, the remembrall's importance has been revealed I think: He was at broomstick flying class, and yet he had forgotten Newtonian mechanics and thus failed to see they didn't apply to broomsticks.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.