I'm confused. I'd assumed that brackets in quotes were to add words for the sake of clarity, not substitute them. So I would have assumed the original quote to

I'm confused. I'd assumed that brackets in quotes were to add words for the sake of clarity, not substitute them. So I would have assumed the original quote to have been "go home and bite pillow". In such cases, is there a different style (perhaps different brackets?) to indicate an insertion rather than a substitution?