Supposedly you needed to be 18 to use the whispers function on Twitch. Knowing that it would be fair to assume that Doc did not know that the person was underage (unless they had a conversation about it).
There are going to be people on the side of "He's a creep PDF file" and "Doc did nothing wrong".
Until we see the content of these messages and key things are made clear, we really don't have a real grasp of what happened. We may never know.
The anonymous email says the conversations were centered around business and how to scale up new twitch channels. Inappropriate messages could be as innocent as Doc telling this individual to use their sex appeal to gain a following (a tried and true method to gaining twitch channel success quickly).
Fair advice, but creepy if Doc knew she was underage. But then again, we don't know if Doc knew this individual was underage. And until the content of the messages is made available, it's fair to assume that a platform in which you had to be 18 to use, that Doc would have assumed the individual was of age.