We believe that your issue has been closed by the upload of
Version 0.9.15 of grml-autoconfig from Michael Prokop <mika@grml.org>.
The explanation is attached below

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Format: 1.8
Date: Tue, 26 Oct 2010 22:55:49 +0200
Source: grml-autoconfig
Binary: grml-autoconfig
Architecture: source all
Version: 0.9.15
Distribution: unstable
Urgency: low
Maintainer: Michael Prokop <mika@grml.org>
Changed-By: Michael Prokop <mika@grml.org>
Description: 
 grml-autoconfig - main bootup process of a Grml (based) system
Changes: 
 grml-autoconfig (0.9.15) unstable; urgency=low
 .
   [ Christian Hofstaedtler ]
   * [a9ef28a] fix handling of multiple console= options.
     [Closes: issue916]
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 f19d2796d94104cbb6b4a422c16dd1f2ea295e5a 71409 grml-autoconfig_0.9.15.tar.gz
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Fixed with a9ef28a9082b24866dcbd5769dcc6c51f09b4ec3 in grml-autoconfig.git.

ACK, no objections against removing from my side.

This can probably be made idempotent by dropping the fallback for console=ttyN 
(sans S). What is the point of the fallback anyway?

Using "console=tty1 console=ttyS0" for booting generates a broken /etc/inittab, 
resulting in (c/p of a serial connection):

 * Bootoption for serial console detected:
 * Warning: console=ttyS... not specified as last console= option. Fall  [ ok ] 
to set up ttyS0/9600.
 *   Activating console login on device tty1 with speed .                [ ok ]
 *   Activating console login on device ttyS0 with speed 115200,57600,3  
[ ok ]00,9600,4800,2400,1200.
INIT: /etc/inittab[71]: id field too long (max 4 characters)
INIT: /etc/inittab[72]: duplicate ID field "T0"                          [ ok ]

Executing:

  . /etc/grml/autoconfig.functions
  config_console

then once again generates further broken entries in /etc/inittab. The code 
should handle the tty* options in the cmdline accordingly and has to be 
idempotent.