FYI I’ve gotten around this by rewriting the HTML with JS on load, but it’s not ideal as updates to the topic won’t be reflected:
$(".category-list tr[data-category-id='5'] .category-description").html('Lorem Ipsum<ul><li>Bullet 1</li><li>Bullet 2</li></ul>');
I’ve also found another topic with the same question: How to show more than one line of the category description when viewing from parent category