Earlier quoted context omitted.
>As a personal note, I know I’m a bit of an exception ...That’s critical for me, and if an ISP filters based on source, it’s a deal-breaker—I’ll switch to a different ISP. "...and obviously, Pennywise, I must spoof ingress and egress..." "Of course, Agent Bond."
If it's your real IP, it's not spoofing, even if you send the packet through a different ISP than the one which gave you the IP. If you think about it: if you got an IP directly from ARIN you wouldn't have to send your packets through ARIN to make them legitimate.
there is no "ingress," just a firewall of bad peers.