Harry tried to imagine all his private thoughts laid bare to someone else. He decided he would make a pretty pathetic picture, which only caused him frown harder. Gaius would never hurt anyone on purpose, but here was Regulus, not only missing his pet, but feeling exposed as well.
"I- there's nothing I can say to make that better," Harry admitted, covering Regulus' hand with his own. "You already know Gaius would never betray you. But I do understand what it feels like to confide in- well, something you think is safe to talk to only to have it be real and human and knowing everything about you."
There had been many events in Harry's life that brought him extreme pleasure, but few matched the fierce joy of plunging that fang into Riddle's diary.