A quick follow up on the original post. We have enhanced our email scan filters a bit so that now they can catch your flagged/starred messages.
This way by a flagging/starring a message in your mailbox you can forward the thread into Highrise and automatically create a follow-up task for it.
You need to use the special tag 'task:<email>:<taskPrefix>', where the email will define who the task is assigned to in Highrise (a user with the email needs to exist)
Let me know if you would like to give this a try.
-Alexey