This can't be anything more than just a fake way to attract new subscribers for the channel. There is no way to include new text within live video streaming. This video is just a pre-made and people are posting their addresses madly but if you check for the winning address, you can't find it in chat area.
You cant be more wrong.. that YOU can't do it doesn't mean someone can't do it. Go to the video and every time you write "free bitcoins" on the chat you will see your name on the video. Also when payment is sent they show on the video too and post same transaction ID on the chat.