Thanks for trying Fabrication. And sorry about the "simple_routing" demo. That demo started off as a basic demo. But the different routing features have grown in size and I am afraid that demo is a little complex now.
still have no idea where is listening for respondToShellMessageCountProxy created.
SimpleModuleConstants.SHELL_MESSAGE_COUNT_PROXY seems has the right syntax but can't find where is implemented as note name.
To answer your question. The missing link is that notifications can also be handled via registering them with commands. The startup command of the module does this,
As a result the UpdateMessageCountsCommand is fired when the RECEIVE_MESSAGE notification is routed into the module. This command then increments the corresponding proxy based on the source of the notification. Hope that helps.