Project Chat and Annotation commenting.
Chat feature is a there when you want to instantly work or discuss with any of your project's collaborator.
A Chat thread can be started on a whole project or on a single comment. When a thread is starting, you are instantly notified in the Global Notification Center and a single click opens the chat you want to reach. You can chat within a public space or a private space with anyone involved in the project with single click.
Anytime, you can get back for any history purpose in any of the started or finished thread.