How do I update Task Status via email?

The Knowledgebase says that I can add a task status to a project via email. But it does not give any instructions regarding syntax, how to format the subject line, etc. There are several other "to add a xxx" items in the article that do include all the details of how to format the email.

What I'd really like to be able to do is have a Task User update the Percent Complete or Add a comment to the Task, but there's nothing showing if that's possible.

From the article:

Now, open your email and start adding your project activities in one click.

To add a status - Copy the email address given in the To Add Status section to your To address.
To add a task - Copy the email address given in the To Add Task section to your To address.