The bug
The text information about a world (like the game mode, the cheats...) exceeds the rectangle, especially when the name of the version of Minecraft is too long and/or when the name of the world folder is too long.
How to reproduce
Load a world into a version with a long name (like 1.14 Pre-Release 1 for example)
Then, look in your list of worlds the line where there is information (such as the game mode) on your world
→ ❌ You will see that the text goes beyond the rectangle (see screenshots)
Example
Here is an example:
Can confirm in 20w51a.