Whether to mark the current user as typing in the thread. The typing indicator expires after 3 seconds, so to continually show the indicator it needs to be called on an interval. Passing false is a no-op and the indicator will time out normally.
A URL where the thread can be seen. This determines where a user is sent when they click on a reference to this thread, such as in a notification, or if they click on a reference to a message in the thread and the message doesn't have its own URL.