You can only turn off Chat Notifications if you are a Pro or Premium subscriber.

Chat notifications are mandatory for anyone not subscribed to a paid subscription. We want to make sure musicians are compensated fairly. This is why we simply ask you give the musicians exposure and hopefully, click-throughs. 

If you're a Pro or Premium user, you can turn off Chat Notifications by selecting the megaphone icon in the filters menu on the bottom left side of the player or in your settings.

In the Settings, you are able to also set the notification delay. This is useful if there is a latency delay between your stream and chat, or if you are competing in online tournaments which require a stream delay.