We had reply via email in the acs3 ticket tracker and it worked ok (maybe even well) for people reading and sending email from emacs or mutt or other text based email handlers.
It was disaster (or at least pretty unpleasant) when we had
clients using outlook or even netscape to reply with mime attachments, bad html, and awful quoting.
I vote no (at least until someone takes the time to write good
filters to rip out the more unpleasant stuff you will get
with email replies).
