If a player gives themselves a book & quill that has a section sign (§) in it using a function, by using a command like the following...

give @p minecraft:writable_book{pages:["§4I Love Minecraft, and their game is super fun, even if it is filled with bugs!"]}

...moving through the text with arrow keys or the mouse stops the cursor too early, as shown in this image.

If the user attempts to highlight any of the text using their mouse or shift and the arrow keys, the game will crash.

The game crashed whilst rendering screen
Error: java.lang.StringIndexOutOfBoundsException: String index out of range: 84