As the title describes. Specifically, if you launch inside a Gamescope window in nested mode (running on another host display server), then move the mouse in one direction in-world:
For vanilla Minecraft using LWJGL2 (<13.2) it works until the mouse hits the edge of the emulated screen inside Gamescope. After hitting this, moving in the same direction causes stuttering as the mouse is forced within bounds.
For vanilla past LWJGL3 (13.2+) everything functions as normal.
For 7.10 with lwjgl3ify, intense flickering on any mouse movements at all occurs. The same issue affects the official LWJGL3 demos.
As the title describes. Specifically, if you launch inside a Gamescope window in nested mode (running on another host display server), then move the mouse in one direction in-world: