[Fern]

History Traits and Ambidexterity Trait will not show a lock icon when you hold shift and click them to well... lock them.
 
You can see this for yourself by opening the trait menu, grabbing any History Trait or Ambidexterity and then holding shift then clicking them. Unlike most other traits, they won't show a lock when you do that.

[Autumn]

Nor does it show on class traits for the most part, basically any trait that has the old trait icon on it instead of the new one.

[Neus]

This has been corrected.