[Dovecot] Sharing user folders doesn't work when users have periods in names.

[ian+dovecot@comtek.co.uk]

I am using period as an IMAP separator with Maildir directories and I 
cannot share folders where the user has a period in their name.

Suppose I log in as 'some.user' and do:
    SETACL INBOX mailtest at example.co.uk +lrwstipekxacd

/var/mail/virtual/users/some.user/Maildir/dovecot-acl is created, with 
appropriate contents and shared-mailboxes.db gains an entry for 
'shared/shared-boxes/user/mailtest at example.co.uk/some.user at example.co.uk'. 
mailtest is simply unable to see a new folder.

As mailtest 'a LIST "" "Users.*" ' is empty. If I do ' a MYRIGHTS 
Users.some.user.INBOX ' I get 'NO [NONEXISTENT] Mailbox doesn't exist: 
Users.some.user.INBOX' and, oddly, a new maildir appears: '* LIST 
(\Noselect \HasChildren) "." "Users.some" ' -- it also creates an empty 
folder structure with a single file 
/var/mail/virtual/users/some/Maildir/dovecot-acl-list too!

Is there a workaround that does not involve rebuilding every user's 
Maildir with backslash as a separator?

Thanks,

Ian