Dear Myron,
You raise a good question, but I don't think there's a hard and fast rule.
I use my judgment about whether my reply to a message has enough context for
someone to understand what I'm referring to.
I delete the original message if there's one clear subject matter indicated
in the subject line. If not, I include the original message so that someone
reading my message can see what it's about. Sometimes the message being
responded to occurred a while ago or in a flurry of other threads. I find it
useful to glance at preceding messages to get the context of the current
message.
SHELL-RELATED QUESTION: Anyone know whether Nannodiella vespuciana and N.
oxytata are still considered synonymous?
David Kirsh
Durham, NC