Minecraft 1.13, Minecraft 18w30b, Minecraft 1.13.1
64-bit Windows 10
In Minecraft 1.13, I'm experiencing a lot of mouse "jitter". It feels as though that the mouse aiming/looking is at roughly 20 frames per second or so (although the issue seems to "simply" be big jumps in the aiming 20 times per second), while the rest of the game (even including player movement!) runs at 60 frames per second. If I switch from fullscreen to windowed mode and/or disable VSync, the jittering is reduced a lot, but I can still see it if I pay attention.
In Minecraft 1.12.2, I seem to experience the same amount of jitter as windowed 1.13, regardless of whether I'm playing 1.12.2 in windowed or fullscreen with VSync enabled. Yes, this is true even if I switch back and forth between 1.12.2 and 1.13, I'm not just talking about my memories from 1.12.2.
While I have a video of the issue, I have not attached it to this bug report, since I can only attach files up to 10 megabytes here (and the video fills nearly 300 megabytes) and I'm too scared that a reduced bitrate or resolution will mask away the issue. However, I have uploaded it to YouTube, where I can see the issue very clearly: https://youtu.be/UlAk4xSLjUg (Make sure to watch it in 720p or 1080p to get a 60FPS video. Also keep in mind that you can pause the video and press the comma and period keys to step through the video one frame at a time.)
Note that at 0:23 in the video, I enable the smooth "cinematic" camera in Minecraft. As the jittering persists to the exact same degree, this proves that the issue is with Minecraft, not my mouse. And at 1:02, I switch from fullscreen to a maximized window, showing the greatly reduced jitter, which is also how 1.12.2 looks both in windowed and in fullscreen.
Edit: This issue also occurs for me in 17w43a, the very first snapshot for 1.13. As that snapshot contained a patch note for updating the game to use LWJGL 3 instead of 2, I assume that the issue has something to do with LWJGL 3. If there's a way for me to make 1.13 use LWJGL 2 to check if this is the issue, please let me know.