Very often as part of an ongoing conversation with a client it's helpful to keep the conversation going by including the entire email thread.
Currently this can only be done through an outside email client like Outlook or Gmail. Why not simply add a "REPLY" option to the actions drop down menu in the timeline for any email in the timeline AND/OR for any form submission?
If someone submits an online inquiry form and you see that form in a timeline, I would want to be able to do something like have a workflow and a task to assign me to reply to that inquiry. I could just go to the timeline, find the form submission and click to REPLY to that form submission. Below my signature all of the publicly visible form fields would be listed so their original question is part of the email thread.