In theory, Obliviations and False Memories can be broken, right?
Where'd you get this idea? As far as I know, the last word we had on that was
The courts use Veritaserum, but it's a joke really, you just Obliviate yourself before you testify and then claim the other person was Memory-Charmed with a false memory. If you've got a Pensieve, and we do, you can even get the memory back afterward. Now, ordinarily the courts presume in favor of Obliviation having occurred rather than more complicated Memory Charms.
That doesn't sound like it's possible even in theory to detect, let alone remove, Obliviations or False Memory Charms.
I was reading the quote you cite as "too much trouble usually" rather than "absolutely impossible", because canon indicates that both can be removed, albeit not easily:
EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
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. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
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, ten.
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: