At CCtoMany, our default configuration for discussion lists is to set the "Reply-to" header to only the original author and NOT the entire list. Recipients can still use the "Reply-to-all" feature of their email program to reply to the entire list if they prefer.
By definition, discussion mailing lists are intended to foster discussion amongst the subscribers. For this reason, some lists want replies to go to the entire list instead of to just the original author. Contact us if you'd like your list configured in that way.