Harry Potter's Use of the Half-Blood Prince's Potion Book

[seldonp38]

HARRY POTTER'S USE OF HALF-BLOOD PRINCE'S POTION BOOK

During my recent reading of the 2005 novel, "HARRY POTTER AND THE HALF-BLOOD PRINCE", I came upon the following passage in Chapter 12 called, "Silver and Opals":

"Harry had already attempted a few of the Prince's self-invented spells. There had been a hex that caused toenails to grow alarming fast (he had tried this on Crabbe in the corridor, with very entertaining results); a jinx that glued the tongue to the roof of the mouth (which he had twice used, to general applause, on an unsuspecting Argus Filch); and perhaps most useful of all, Muffliato, a spell that filled the ears of anyone nearby with an unidentifiable buzzing, so that lengthy conversations could be held in class without being overheard. The only person who did not find these charms amusing was Hermione, who maintained a rigidly disapproving expression throughout and refused to talk at all if Harry had used the Muffliato spell on anyone in the vicinity."

I am curious. Did anyone find this passage amusing? Did author J.K. Rowling expect all readers to find this amusing, because the novel's main character, Harry Potter, was the one committing this deed against those he did not view as a friend or ally? I wonder.