I forgot to mention yesterday that, as I'd mentioned several months back when we were dealing with Angelique's funeral, after I'd seen NoDS for a second time, I was certain that Laura was laughing at the funeral because Rev. Strack characterized Angelique as Laura's "loyal and loving sister-in-law" and Angelique had been anything but. And as I'd also mentioned back then, when I finally got my hands on a copy of the script back in the early '90s (through the generosity of a good friend), I was honestly quite surprised that the script has its own explanation, and that explanation just came up at the end of Scene 229:
Page 106/Scene 229 - Quentin: 'So this is why Laura was laughing at the funeral. They were burying an empty coffin.'
And while I can see the humor in that explanation, I don't know, I still like my interpretation because it's humorous in an Oh-My-God-You've-Got-To-Be-Kidding sort of way. And considering that Scene 229 doesn't appear in any version of the film, the reason for Laura's laughter is still left up to interpretation. In fact, in the current version of the film, many things are left up to interpretation, with another example coming up fairly soon...