^{Updated from EVGENSYPERPRO}
Summary:
Bold text (§l) sometimes goes beyond the text field. This happens with a large number of characters in the second and next lines. Applies to chat, signs, books.

Steps to reproduce:

1. Write in chat, sign or book several lines of bold text.

§laaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Observed results:
The text on the second (and next) lines goes beyond the text field.

Expected results:
The text will not go beyond the text field.

Original description:
Note: I am using a 21:9 monitor.
The image should give you all the details.
Bold text sent in chat using §l will leave the shaded text area if a word is long enough (i spammed Q).