Voldemort might have vanished for ten years intentionally. It's certainly within his power to reveal himself to his old followers now, and probably take charge of them again, but he hasn't done so. Whatever his intentions are, it seems they're probably not served by people being aware that he's still around. Who knows how long he's been possessing Quirrel?
That wouldn't make any sense- by doing so he loses a lot of followers (Bellatrix at least was imprisoned), allows the enemy to regroup, and would make them more hopeful of winning the next time. (Who's going to believe him, after all?)
- 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.