Harry ignored her. He had just found an incantation (“Religo!”) scrawled in a margin above the intriguing words “For Enemies,” and was itching to try it out, but thought it best not to in front of Hermione. Instead, he surreptitiously folded down the corner of the page.
Or: why Hermione was right about the dubiousness of handwritten spells, especially when Harry was concerned. He always seemed to make the unexpected happen.