Least convenient possible world for your objection: the protagonist couldn't change her liability to shut up, but could change her rationality.
That's possible, but so unlikely that it strains credulity (haha). Like I said in my reply to Kaj Sotala, this story is trying to make a point about some humans who live in the real world. Have you ever heard of someone for whom changing from a 'hyper-rationalist' to a deluded fool is easier than to learn to keep one's mouth shut every now and then?
Poignant short story about truth-seeking that I just found. Quote:
The full thing reads like a flash tour of OB/LW, except it was written in 2001.