What i find interesting about this article is not the realization that MPI is like email, but the reverse, that human collaboration using messages is like MPI. The suggestion to use SMTP as a transport for things much more complex than emails is something worth looking at. It relates to my belief that the instant messaging difference does not come from the new protocols like XMPP for jabber, but from the new client interface that facilitates short messages in a conversational style. SMTP is equally (if not more) capable of transporting these messages. Sure, SMTP is not designed for "instant" messaging. but todays use of SMTP where my local SMTP server talks directly to your SMTP server, makes email is just as instant.
We don't need another protocol, at best we need improved SMTP servers that handle multicast messaging. But the sender/recipient envelope is as simple and timeless as it gets. Any additional data can be added in headers, and here is where there is plenty of room for change.
We can make email messages more sophisticated, with additional headers indicating for example whether a message requires an action, or a response or whether it is merely informational. A reply message could then contain headers to show if the message is a response, or a followup question, or just an acknowledgement of the original message.
All we need for this is to add these features into email clients to allow more sophisticated messages to be sent and received.