When you add a meta box to Gutenberg, it looks different than the other items in the editor. There is a HR, and the fonts are different.

Does anyone know how to fix this so it looks like a natural part of the site, and not “some junk Automattic didn’t add”.

Example code:

function myMetaBox() {
    add_meta_box(
        'MyMetaBox',
        "Why the odd font?",
        'myBoxOutputCallback',
        'post',
        'side'
    );
}

add_action( 'add_meta_boxes', 'myMetaBox' );

function myBoxOutputCallback(){
    echo ("Gutenberg is a great addition! NOT!");
}