Retail:
Shadowlands:
See all Retail and Shadowlands versions here: https://imgur.com/gallery/ZWeZBcB
So, if I were to guess, it looks like maybe a hair texture used to cover the upper lip as well as the mustache mesh actually being positioned at a different angle.
It's been like this for ages now and I'm worried it's permanant.
Not a fan of this change personally, are you? Is this intentional or just something they've overlooked during the revamp?
edit: maybe the mesh angle position isn't even different. Looking closer on retail ingame, it's clear there is a fur texture on the upper lip that isn't applying with these new settings on PTR.