We all know that while his helmet is active, Mysterio is immune to concussion and any AAR.
Well... I found out that, against the Glancing mechanics, he suffer from ability reduction.
Video proof here: at 60 seconds I land my 5th hit, a medium hit. That hit has been glanced and I didn't receive my chemical gas.
https://streamable.com/nhitdPS: sorry for the awful video quality, I'm poor