[Dovecot] Making shared folders "unmovable"

[Dave]

 > By default Dovecot doesn't allow using the IMAP "anyone" or
 > "authenticated" identifier, because it would be an easy way to spam
 > other users in the system. If you wish to allow it, set:
 >
 > plugin {
 >   acl_anyone = allow
 > }

Greg, thanks for your reply, I missed that in the wiki about the 
"anyone" identifier.  I will try that setting that you mention, BUT I 
don't know that it will work because before I tried using "anyone" as 
the identifier I tried using the username I was logging into the account 
with (using the "user=" parameter in place of "anyone"), and that didn't 
work either. :(

...

OK, I tried it with the username I use to login to the account instead 
of "anyone", and with "owner" as Timo suggested (thank you as well), and 
neither of those worked.  My dovecot-acl contained "user=dave lrwstipea" 
in the first case and "owner lrwstipea" in the second, and neither is 
making a difference, I can still rename/delete/etc that folder.  Any 
other thoughts??  I don't need to restart dovecot or reload the config 
or anything if I make a change to the dovecot-acl file do I?

David