My 2 cents:
I prefer the default be munging of the "Reply-To:"
header also. It is more convenient for me. Replying 
to the sender only is a special case, and IMHO 
deserves to be handled that way.

RFC: I don't know.
 
>>> lxy at cloudnet.com 02/26/02 11:12AM >>>
>>On Tue, 26 Feb 2002, Carl Wilhelm Soderstrom wrote:
>> as for me, count me in on the side of munging the Reply-To: header. makes
>> replying to the list much more convenient. I hit 'reply' to reply to the
>> list; and if I feel like personally bothering the original poster with my
>> drivel, as well as the list in general, I hit 'reply to all'. 
>> these are the common cases.
>Hmm.. this goes against what I perceived to be the general mailing list
>logic.  To reply to the sender, hit reply.  To reply to the list, reply to
>all.  This is the way I was taught to set up lists and they way I always
>do it.  I thought that was just kind of accepted as the method everyone
>used.
>Is there an RFC on this anywhere?