Maybe KMail or Opera Mail (as our another member tested) would detect that this is a mailing list mail and automatically reply to list, while GMail only see if the mail contains Reply-To header.

2011/2/24 Oliver Burger <oliver.bgr@googlemail.com>

Am Donnerstag 24 Februar 2011, 14:05:47 schrieb Michael Scherer:

> Le jeudi 24 février 2011 à 16:48 +0800, Franklin Weng a écrit :

> > However, when I click "reply", I found that the reply address was set to
> > the sender of the mail, not to the mailing list.

> And so, basically, in the end, the IETF answered about the usage of
> Reply-to:, explaining its use, and so saying this should not be used for
> forcing people to answer to the ml.

And no matter on which mageia ml (I am reading quite some) I klick on the
"reply" button in KMail, it's answering to the list, not the author of the
mail I read.
Could this be a problem with your mail client?

Oliver