Interesting debate.  To bring this into discussion of RCD, just which of the many list headers does Roundcube support?  See http://www.rfc-editor.org/rfc/rfc2369.txt  I note that this email uses the List-Id header to identify the list.  On gmail's web client, gmail does not detect this and a reply goes to the sender.  In thunderbird, I have the option to reply-list, reply-all, or simply reply.

Also, for anyone reading the debate, I would point out that Marc Merlin's assertion: ", RFC 2822, which states "When the "Reply-To:" field is present, it indicates the mailbox(es) to which the author of the message suggests that replies be sent." (notice author, and not list software)" is no longer correct.  Time marches on, and in http://www.rfc-editor.org/rfc/rfc5321.txt we have in section 3.9.2

   When a list constrains its processing to the
   very limited set of modifications and actions described here, it is
   attempting to emulate an MTA; such lists can be treated as a
   continuation in email transit.
   There exist mailing lists that perform additional, sometimes
   extensive, modifications to a message and its envelope.  Such mailing
   lists need to be viewed as full MUAs, which accept a delivery and
   post a new message.

As this particular list appends a signature to the content of each message it sends, it could be argued that it is acting as an MUA and posting a new message, and hence is the author of that message.

RFC 5589 provides a good summary of current practices:
http://www.rfc-editor.org/rfc/rfc5598.txt

Note, this rfc is Informational, so it is not setting any standards.


He fails to account for
On 11/30/2010 6:35 AM, Raoul Bhatia [IPAX] wrote: 
On 11/27/2010 12:37 PM, Andreas Dick wrote:

 hello
 I am wondering why the reply address is not the dev@list if I write to 
 the list, as I know it from other lists... is this not an admin setting 
 of the mail list admin?
 this would help a lot to make open discussions.
 Andreas

wars are waging over this since ages:
   http://marc.merlins.org/netrants/listreplyto.html

cheers,
raoul