Even obliviation seems weak: perhaps there are ways to be unobliviated ex-post.
Canonically, IIRC, obliviation can be broken by sufficient torture.
Canonically? Where?
The only thing resembling actual "unobliviating" that I can think of is Lockheart apparently slowly slightly recovering from his memory charm blowing up in his face via the broken wand. And that was after several years of ongoing treatment at St. Mungo's.
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: