Although Dolores Umbridge is highly unlikable from the very start of
Harry Potter and the Order of the Phoenix,
in these chapters she proves just how evil she can be. Instead of assigning a traditional detention and forcing Harry to write regular lines, Umbridge has Harry carve “I must not tell lies” into the back of his hand, a cruel and unfair punishment. Both Ron and Hermione suggest that Harry complain about his detention to Dumbledore, but Harry refuses. He is still upset with Dumbledore, but he also doesn’t want to show any signs of weakness, particularly in front of Umbridge. That Harry neither complains nor tattles again confirms why he was placed in Gryffindor, not Slytherin: he bravely endures Umbridge’s petty torture, without a word of complaint.