Possible Clues:

• It betrays unconscious desires
• Mistake revealing hidden concerns
• Perversely, I find pleasure endlessly revealing error
• Silly friend Paul is making a revelatory mistake
• Unintentional error
• Revealing though unintentional expression of a sinful pride, perhaps
• A sinful pride that's woeful -- it exposes an unconscious thought?
• Kind of shrink underwear giving revealing glimpse!
• Error betraying unconscious thoughts
• Perhaps 1p under fails, giving away more than intended