Status Proof is one of 3 Mercenary's possible traits.
It gives the Mercenary the ability to regenerate from status effects 2x faster than normal. It is most effective with Fire, because it expires quickly, and with the trait it takes just few HP. It can also stop a soldier with the ice effect from freezing. However, it can't stop the killstreak Satelite Beam from taking effect, as it freezes instantly.