“Forwarded the above email” banner

Continuing the discussion from Text of forwarded emails don't show up in posts:

I have rules set up in outlook to forward into per sub-category inbound email address on discourse.

I have auto-create staged users disabled, because people who email me don’t want emails from my private discourse. Fortunately the staged user is kept constant by not re-directing the email (or using mail forwarding rules in outlook).

However, a banner appears with the same staged user, it looks like;

I’d like to learn more about what this banner replaces, and whether it can be turned off?