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I lied, here's the next one and it's short still:
Dear Lily,
I've gotten your reply to my last letter and let me say something: HOW DARE YOU INSULT MY GREAT-GREAT-GREAT-GREAT-GREAT (more greats) GRANDFATHER LIKE THAT! Salazar Slytherin was the only Parsletongue and it's not possible for anyone else to have that ability, how dare you even imply something like that! How dare you try and defy what I know, how dare you insult my knowledge, and even worse, how dare you suggest that it means that me and your brat are related in some way!
This shall be added to my list of reasons to kill you:
Reason 99: Insulting my knowledge of Parsletonguery.
The only thing I regret is that I can't kill you again because you are already dead so now I need you to live so I can kill you for the above reason.
Lord Voldemort