Luna takes her job very seriously. When she hears there's a human having difficulty sleeping, she decides to share a bed with him until he feels safe and happy again.
Despite their detached relationship, Thorax never gave up on his brother. With Pharynx now transformed, his cold demeanor has begun to thaw, and so Thorax is presented with something he's never had, before - an interactive big brother.
Luna has hidden a deep, dark secret from the ponies she watches over so lovingly. Were they to discover it, she can only imagine what it would do to the image they now hold of her. Twilight thinks it's just precious.