I can't really add much to what's already been said here. Like most of you, I didn't actually know Harris but still feel an incredible sadness. He always made me laugh unlike almost anyone else. His humor was so smart and dumb at the same time, and he was so quick with a joke. I always liked seeing his name pop up on an episode in the morning when I checked my feed.
Part of my sadness is knowing that we will miss out on decades of comedy from him, but another part is knowing that he was going through an incredibly difficult time battling addiction. Similarly to the Robin Williams tragedy (albeit a different situation), I am always saddened by the idea of those who can bring so much joy to so many, while struggling to find peace in their own lives.
I heard Harris talk about his addiction on Pete Holmes' show a few months ago. It was sad (but typical Harris, also very funny in parts) to hear him talk about what he had been going through, and I held out hope that he was finally going to beat it. When I heard the news Friday morning, my heart just sank.
So, I feel like I've lost a friend, even though we never met. His friends and family are in my thoughts and prayers.
RIP, Terrorist Wittels. You will be missed.