I find it more likely that he tinkered with the object itself, if that's even true.
I wonder if Quirrell could have managed to get a fiddly thing of his own invention into the headmaster's office before Dumbledore took over for Dipot. Perhaps as a gift to the old headmaster. It'd be an incredibly useful source of knowledge, if Wizards do in fact have magical listening devices.
You'd expect the Headmaster's office to be laced with anti-eavesdropping charms.
(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: