Hi Jason
We don't have a specification for how our messages work, and not even a blog post!
I am not sure if designing again we would do it exactly the same, but its a bit like facebook whilst keeping the underlying database structure and functionality of Moodle messages.
You see up to five messages in the dropdown- latest first.
if you select "see all messages" you get a page like this:
You can reply, go to contacts or choose to compose a new message. In which case you search for the message recepient:
Then compose:
The only message settings you have is whether to forward messages to you email account:
Is that what you wanted?