Mariah's video is replicating the visual artifact I am experiencing.
Why was this marked as resolved? I don't see any attachments included or more details other than what Monica added. This is definitely a visual bug. I saw it when I tried the snapshot and should've reported, but here we are.
I'm on a 2012 Macbook Pro. When moving in any direction there is a, for lack of a better description, pixelated line or blur that appears in the bottom third of the screen, just above the hot bar. This visual anomaly occurs when moving backwards, forwards, or side to side. It also persists no matter the texture pack. I was using Default 32 and Default 32 3D Add-on. Switched to the stock delivered texture pack and the visual anomaly persisted.
Another way to put it is it looks like a Minecraft-y version of a heat mirage. Very distracting and very much happening. When I first noticed it during the most recent snapshot I immediately switched back to 1.14.2 and the bug went away.
I will be attaching screenshots with the debug screen present, however, the screenshots are not capturing the issue. It appears as if the visual bug is not captured by the screenshot functionality. This may require further testing by others to replicate. That being said, this is a real bug and is affecting gameplay.
I was able to confirm what Stacey posted: disabling VSync mitigates the issue. Works as a temporary fix, but not great as a permanent setting on older machines. Also, as Stacey pointed out, this was not necessary in 1.14.2.