Luis von Ahn is the CEO of  Duolingo. He blocked pm on Twitter but we can reply to his tweet of him happily announcing Maths Duolingo. There are already replies asking for a revert or a toggle to the skill tree. You can join the party here: https://twitter.com/LuisvonAhn

I also found him on Facebook, and sent him a message. And I'll try to find an email address.

At next milestones, we are sending emails to Duolingo's investors. Please keep sharing on all platforms!