If my assumption about webmail is correct [...], it might be good to have Reply-all as 'default' - keeps discussion in the community.
The first result for the DuckDuckGo link (which thanks to filter bubble popping will be the first result for all of us) that Sam posted convinced me I was wrong, because it mentioned my argument almost verbatim and then refuted it. Apparently there is a better way, technologically speaking.
Email seems like such an underutilized (by the average person) technology, too. There is quite a lot in there...