Harry Potter and the Zeugmatic Sentence

While waiting for my English language version of the latest Harry Potter to make its way across the ocean, I’ve been reading the fifth book again. And I’m still amazed at how little happens in so much space. An editor may have helped. But maybe an editor would have insisted on removing sentences like this (page 127 of the English edition.)

bq. Dumbledore was striding serenly across the room wearing long midnight-blue robes and a perfectly calm expression.

That sounds mildly defective doesn’t it? Wearing robes isn’t the same kind of thing as wearing a calm expression.