Stupidity: When Malfoy gets into trouble while trying to catch Harry with Norbert, Professor McGonagall dismisses his claims as "utter rubbish", and a "cock and bull story." To prove his story was true, Malfoy could have shown her the letter Ron received from his brother Charlie (which Malfoy accidentally received when he borrowed a book from Ron), which detailed their plan to deliver Norbert to Romania.
Continuity mistake: Harry buys the book "One Thousand Magical Herbs and Fungi", but later, the title changes to "One Hundred Magical Herbs and Fungi".
Question: Has it ever been explained what happens to a wizard/witch if they don't repay a life debt? Harry should owe one to Snape after Snape rescues him from Quirrell's curse during the Quidditch game, but he never does throughout the series.
Answer: It does not appear that life debts automatically form whenever somebody saves somebody else - J K Rowling has, for example, stated that Ginny did not incur a life debt to Harry when he saved her in the Chamber of Secrets, although she said nothing about what circumstances need to occur for a debt to exist. In Snape's case, there would seem to be several possibilities. 1) A life debt simply didn't form. 2) Snape is protecting Harry because of his love for Lily and his failure to save her, so he may actually be paying off a debt of sorts himself by doing so. 3) Harry's father James saved Snape from almost certain death when Sirius tried to trick him into going into the Shrieking Shack when Remus Lupin was in his wolf form. As such, Sirius may have owed James a debt, which he paid off by saving Harry. 4) A life debt did form but, as Snape died before Harry could pay it off and, insofar as we know, had no relatives that the debt could pass to, Harry was let off the hook.
Tailkinker ★