dovecot - Oct 2013 - Questions about special_use mailboxes

Hello,

I am using using dovecot 2.1.7 from debian stable:

namespace inbox {
  inbox = yes
  location = 
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Spam {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = 
}

I monitor IMAP traffic using the MUA trojita. When I select the mailbox Drafts:
>>> y10 SELECT Drafts (QRESYNC (1381746443 1))
<<< * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
<<< * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)]
Flags
permitted.

Flag is \Draft instead of \Drafts?

When I select Sent

 >>> y12 SELECT Sent (QRESYNC (1381746442 7 (2 2)))
<<< * OK [CLOSED] Previous mailbox closed.??
<<< * FLAGS (\Answered \Flagged \Deleted \Seen \Draft $SENT)
<<< * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft
$SENT \*)]
Flags permitted.

Why is the flag $SENT ? http://www.faqs.org/rfcs/rfc6154.html mentiones nothing 
like that.

When I select Spam:
>>> y14 SELECT Spam (QRESYNC (1381746444 1))
<<< * OK [CLOSED] Previous mailbox closed.
<<< * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
<<< * OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)]
Flags
permitted.

No flag at all?

Or am I getting IMAP wrong?

Thanks,
Florian