Hermione ripped open the newspaper and began to read the report inside while Harry looked around the Great Hall. He could not understand why his fellow students were not looking scared or at least discussing the terrible piece of news on the front page, but very few of them took the newspaper every day like Hermione. There they all were, talking about homework and Quidditch and who knew what other rubbish, when outside these walls ten more Death Eaters had swollen Voldemort's ranks.
Harry Potter and the Order of the Phoenix
I'm wondering why it puts a comma between 'were' and 'talking'. I think "There they all were talking about homework" is fine. Another thing is about "who knew what other rubbish", which I feel it should be "who knew what other rubbish was". Any thoughts?