OK, so I think I’m finally learning –
If create_replies is the chosen value for the forwarded emails behaviour site setting, then the original message becomes the opening post in the topic, and anything written in the email above the forwarded message, becomes a reply to the topic below the 3rd party message. 
Q: Do any of the other values of this site setting – namely, hide or quote – just (only) process the original 3rd party message and nothing more?
I am wondering if the attempt to split out these “create replies” might be the cause of some weird errors I’ve been seeing when sending things in from a Microsoft Outlook client.
PS: I wonder, might this setting be worth a FAQ/howto entry to be linked from the description text below the site setting? It might just be me but I have rarely been so confused with a Discourse setting over the past 7 years. Or maybe I just need more 
