If the mailing list replaced Reply-To header it would required additional effort for responders instead of just pressing reply-to- all.
If the list were to add a "Reply-To:" header, but only in the case where one was not already present, that would seem to me to be ideal. (None of the internet polemics against Reply-To that I have seen, have considered this modest suggestion.) In the past, I have carefully used the Reply-To header to direct responses to a particular mailing list of many (e.g. when cross- posting an announcement). Yet because there is a culture of "Reply- To: is bad", and most MUAs do not have a "ReplyToList" option, most respondents end up pushing "Reply to all", which ignores my setting of "Reply-To:", and spams more people than necessary. Regards, Malcolm