gistfile1.php

add_filter( 'author_link', 'prefix_adjust_author_link', 10, 3 );
function prefix_adjust_author_link( $link, $author_id, $author_nicename ) {

	$author_id = intval( $author_id ); // Sanitize
	$user_info = get_userdata( $author_id );
	if ( ! $user_info ) {
		return $link;
	}

	$link = home_url( '/' ) . 'who/' . $user_info->user_login;

	return trailingslashit( $link );
}