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.