Puckdropper puckdropper(at)yahoo(dot)com wrote in
eb.com:

Trouble is, those are the idiots who are doing the programming!
Yahoo! Groups is terrible about this, and many of the iPhone email
messages I get don't have quoted text, which tells me it's off by
default.

I have seen people say that quoting can't be done on the
iPhone/iPad, which tells me that if it can, it's not easy
(it's probably a Jobs thing - he wasn't interested in
anyone's thoughts other than his own).

I don't think including context is possible in Yahoo Groups
if you reply in the Group. You have to do it in email.
Altho Yahoo seems determined to make Yahoo mail totally
disfunctional, so maybe you can't do it there, either,
now-a-days.

John