Asana users have been asking for the ability to communicate privately in a way that Guests/Clients are not able to see.
In this workaround solution, I show you how to achieve Private Internal Communicate via a Private Project.
Here's the issue as described in the Asana Forums:
"I am a project manager who uses Asana for task management and bug tracking for client projects. My company has the premium version so we utilize the private projects feature for internal tasks. However, for the tasks that we share with the client, it would be very helpful if Asana had the ability to add a private comment that only the assigned person would see. For instance, it would be a comment from me to the developer that the client would not see. I use JIRA for a different client and it has that feature which works great. The ability to edit comments also would be a helpful feature."