Version: 1.20.1
Mod Loader: Fabric

Emissive pixels on player heads are not rendered at all
Screenshot of the bug in-action:

(Also sorry if this is bad, this is the first bug report I've ever made)

Yes, this is one of the reasons emissives are still beta. They work by drawing your entire player a second time without lighting using an alternate version of your skin that's just the emissive pixels. To avoid z-fighting, the places emissive pixels were on the vanilla skin are erased.

The way these are rendered has been pending a rework for a long time, likely via GL_POLYGON_OFFSET, but it's not something I've gotten around to.