The "next/prev" links seem a bit awkward and I don't use them as
much as I expected to. However, move the "raw" message link
near the top since it's most useful for checking or reinforcing
the validity of the message via GPG or just reading headers.
Turn the Subject line into a permalink to the message, since
that's probably the common behavior anyways for other messaging
systems. Make the "[threaded|flat]" view links to always
visible for bookmark-ability despite the lack of a "permalink"
label.