In WordPress 4.9.2 auto-formatting of author bios via get_the_author_description was removed after being introduced in WordPress 4.9.
Introducing auto-formatting broke a number of themes. Unfortunately, reverting it in 4.9.2 potentially breaks themes that had implemented a fix for this
For background, formatting was introduced in #40040 and reverted in #42578.
Maintaining auto-formatting
Theme authors wishing to maintain auto-formatting of author bios can add the following code to their theme’s functions.php file.
add_filter( 'get_the_author_description', 'wptexturize' );
add_filter( 'get_the_author_description', 'convert_chars' );
add_filter( 'get_the_author_description', 'wpautop' );
add_filter( 'get_the_author_description', 'shortcode_unautop' );