[quote=@Tarquin]Even better when they have a little extra bit about becoming a super cold badass when they have to be, giving them carte blanche to act as they see fit when they want to stop being friendly.[/quote]

I frequently see the "Character has [Personality trait X] but also is [Diametrically-Opposed Personality Trait Y] in some circumstances". I don't think it's meant to be a carte blanche but an attempt to balance the character and give them some dynamics - although, as you say, it does basically load that character with caprice in the very section that's supposed to make your character comprehensible and reasonably predictable for the GM (and usually other players') benefit.