I was messing around in Minecraft with Creative Mode and ran into an interesting bug with the World Border. When you get into contact with the world border (as in walking, sprinting, swimming, or boat ride) you get stuck in place until you stop moving or walk out of it. This can result in you floating if you press against the world border when airborne.

I decided to test if it had the same effect on mobs and found out that they take suffocation damage from pressing against the world border. (I am assuming that its suffocation damage, because I don't have any idea of what else the damage could come from.) I tried it out in survival but no suffocation damage was dealt to the player.

The world border also had some rendering issues with the new Fabulous option and you can see the world border through the world border even if there's blocks in middle of the view. I hope that explanation made sense, I will post a screenshot and a video of it below. I also tested it in Fancy and Fast and it doesn't occur. I labeled the screenshots Fabulous and FancyorFast and I'm also on the outside of the border to clear up any confusion.

Also heres the link to the video that shows all these bugs in action:
https://www.youtube.com/watch?v=yOEU8uxbNY4