Book signing GUI has broken formatting for right-to-left languages

The bug

The book signing screen of writable books has broken formatting for right-to-left languages because it uses the legacy formatting codes:

• The blinking cursor which is supposed to change colour instead shows a "0" and a "7"
• The author's name is not gray and instead it shows an "8"

See attached Book signing broken formatting.mp4.

How to reproduce

1. Change the language to a right-to-left one, e.g. Arabic (first right-to-left language in the list)
2. Give yourself a book and quill

   /give @s writable_book

3. Open the book and click the button for signing it (left button)
   → The formatting is broken as described above