Possible nnmaildir bug

[Harry Putnam <reader@newsguy.com>]

I hope this isn't a false alarm.  Its a bit hard to tell if it is a
problem with nnmaildir or something else.

The general problem is that gnus doesn't seem to be putting the
warning `Gnus-Warning: [...] Duplicate' on messages with identical
message ids. 

Can this problem be related to nnmaildir?... It seems that it might..

General facts: 

I have two setups that convert news to mail, one using nnml the other
using nnmaildir (both using procmail).  Each on a separate machine.
I'm not entirely sure if these setups are identical in all other ways.
Thats a bit much to keep up with.  And in this case, involving
duplicate messages, gnus has a plethora of functions and variable that
effect that.

So many that the names and doc strings really aren't enough to tell
what they all are supposed to do or if they are set the same in both
instances of gnus.  My best guess is that the ones that should effect
whether gnus puts the `Gnus-Warning:[...]Duplicate..' are set the
same.

Now to the punchline:
It seems only the instance using nnmaildir (todays cvs) is
not putting the warning message on duplicates.

The duplicates are being produced by some bunky clumsyness in my
conversion scripts, as yet unresolved, and has nothing to do with
gnus. I've been just removing them when they occur (seldom).  And
have scripting that finds them by looking for the Gnus-Warning.

Thats how I noticed that warning being absent on the nnmaildir setup.

More general info:

The procmail process in both cases is very similar but not identical.
On the nnml based setup, procmail is writing mbox files that get
slurped.  On the nnmaildir setup procmail is writing maildir style to 
news.group/new.  (a builtin function in procmail).

But only on the nnml based setup is the Gnus-warning being applied to
duplicates.  In both cases the variable is set to default (77)
(C-h v shows - gnus-duplicate-mark's value is 77)

I wondered if the process in nnmaildir that converts incoming messages
from New to Cur may be missing this functionality.