Dave Lers wrote:
> ...I have no idea of the specifics, but there are some email clients
> where that option is/can be automatically
> enabled when message text is highlighted prior to hitting reply,
> e.g. Thunderbird, Claws, OSX/iOS Mail.

Add KMail to that list. I tested Thunderbird, Claws and KMail; all
default to quoting highlighted text. Claws defaults to a bottom
cursor, KMail and Thunderbird to a top. All can be reconfigured.