"I'm not overly noble," Harry argued. "I just care about Faustus and don't want to see him get hurt." That wasn't being overly noble. Though it was true he didn't want Faustus hurt by Severus's reputation, or Severus.
"Prat," Harry called him again. "Really I think we're only friends because you enjoy both insulting me and my house." Though it was fun to banter with Severus.
"Hilly would pop in with a note." Harry reassured him. "I have grown up somewhat and at least one thing I've learned is if you're going to borrow a child make sure parents know if you're going to keep them longer." He laughed softly, "Though I doubt Polly would like sharing the attention with yet another person."