How does mortal spin work?

Question

On bulbapedia, it says that mortal spin leaves the target poisoned. However, in this replay from an ongoing Uber tournament, Ribombee got mortal spinned several times consecutively yet was never poisoned. What is going on? How come it didn't get poisoned?

Answer 1

Ribombee had the ability Shield Dust.
Shield Dust prevents the additional effects of attacks taken. The poison from Mortal Spin is an additional effect, so Shield Dust prevented it.

Source: Just knowledge of the game. Shield Dust is not a common ability, and the mons that do get it are pretty much all terrible, so I can't really blame you for not knowing about it/what it does (except I can haha noob).