Proof email notifications - add a date/time stamp to new comments

Currently, proof email notifications add new comments for the entire comment thread, but there is no way to tell which of the comments are actually new. A date and time stamp to each comment would be helpful when a user is skimming through the email for what is actually new.

In a proof, they have the date/time stamp for each comment.

But when the email notification comes through, there is no way to tell what is new and what has been added to.