A controversial unfair dismissal ruling that held "f------ dog c---" was unexceptional language in the workplace has been overturned after the Fair Work Commission found the decision significantly downplayed the misconduct.

A full bench majority held commissioner Bernie Riordan "mischaracterised" South32 miner and Construction, Forestry, Mining and Energy Union lodge president Matthew Gosek's abuse and threats to co-workers who participated in a workplace investigation, including by calling them "f------ dog, c--- and dog c---" and threatening to hunt down and destroy them.