[Dovecot] Incorrect response when opening read-only mailboxes with per-user flags?

[Guido Berhoerster]

After some debugging on the protocol level I've finally found the
problem with per-user seen flags in read-only mailboxes. Dovecot
actually does allow storing the seen flag on messages but AFAICS
it does not communicate that correctly to clients, this is what
its response to selecting a read-only mailbox with "lrs" ACL in
effect for the logged in user looks like:

2 SELECT "Public/Test"
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
* OK [PERMANENTFLAGS ()] Read-only mailbox.
* 2 EXISTS
* 0 RECENT
* OK [UNSEEN 2] First unseen.
* OK [UIDVALIDITY 1364221612] UIDs valid
* OK [UIDNEXT 3] Predicted next UID
* OK [HIGHESTMODSEQ 1] Highest
2 OK [READ-ONLY] Select completed.

Shouldn't PERMANENTFLAGS contain \Seen here if per-user seen
flags are enable and should it even be tagged READ-ONLY at all in
this case? At least clients such as Python imaplib, IMAPClient,
or Roundcube will open such mailboxes with EXAMINE and thus do
not allow the modification of flags.
-- 
Guido Berhoerster