When I was going to name the rabbit "Killer Bunny" and "Toast" (I was going to rename it "Killer Bunny" again because last time I did it doesn't work so I was trying it again if it works.) on an anvil and when I'm going to rename the Name Tag, and when I press the Backspace key, it doesn't remove a letter. I thought my key is broken until I do it in a Notepad, it does remove it, Same with the chat bar in Minecraft but not on anvils. So, I had to restart my game to see if it still working like normal, turns out it's still had the same issue. I decided to report this issue I was having, and I hope it resolves later.
Later on, when i tried to edit a text by moving the cursor to the left, it did not go anywhere other than typing.
Steps on how it happened:
Grab an anvil and place on any surface.
Grab any kind of item you are going to rename it.
Place the desired item in the anvil.
Try to rename the item into any name you wish.
When you press the Backspace key or move the cursor (the signature "_" / Underscore), it will just sit still.
Duplicate of MC-266886, fixed in upcoming pre release.