b) you are conflating at least two things here - one being whether
people want to get duplicate copies of a message sent to a particular
address (IMHO it's fairly safe to assume that most do not want
duplicate copies), another being whether senders prefer that replies
reach everyone who received a copy of the original message - or at
least, don't mind having this as a default.
Possibly so. But you now seem to accept that the number who find duplicate
replies "obnoxious" is nearer 90% than 50% (which indicates that some
change to protocols and/or practice is definitely needed).
"most" implies more than half. it does not imply nearness to 90%.
As to the number of people who would routinely intend replies to go to all
of the original recipients, even where mailing lists are not involved, I
would expect that actually to be considerably less than the 50% I allowed.
I would expect it to be more than half.
(hmmm. wonder if any of the webmail services keeps stats on such things?)
ISTM that the only reason that people use Reply-to-All when responding to
mailing lists is that it is the only way of ensuring (without inspecting
the headers carefully and cutting/pasting as necessary) that the reply
goes to the list at least.
I don't know why you believe that.
Keith