From Exalted - Unofficial Wiki
Point value: -1 to -3
Nobody's good at everything - the wisest scholar may be unable to ride a horse, and the mightiest warrior unable to lead. But most of them know it. A character with the incompetence flaw is completely unaware of one of their failings, and worse - is quite confident that they are capable. The character must have an ability at 0, or take a negative specialty of -3; the character will believe that they have either four dots in the ability or a +2 specialty. The character is unable to raise that attribute with experience. If the character fails a roll relating to the incompetent pool, they are convinced that it was just bad luck or external factors. Incompetence is worth 1 point for a specialty, 2 for an ability, and an extra point if relating to a combat ability.