When having a long command in a command block, requiring the player to scroll through the information, if trying to copy the text it will not scroll, and the selected text will continue off screen.

How to replicate:
in a command block, hold shift, and a directional arrow and copy a command which extends across the bounds of the text box

The provided image is a command copied from right to left, 1.13 scrolls to the left, whereas 1.14 does not.
(top is 1.13.2, bottom is 1.14 pre-release 1)