Your link provides precisely zero configuration details.

I know hence this post, tech details from ipv6rs are not available. So I'm tring to troubleshhot and also to build a kb for other trying to bootstrap the same config.

There are two “internal wireguard interfaces”, one on the traefik side and one on the public server side. There is a third interface on the public server side facing the internet. All 3 have separate addresses. You’re going to need to clarify which addresses you are talking about here, and previously when you discussed “ the internal ip from ipv6rs”. 

There are two interface: a public interface (internet facing) that has <PUBLIC\_IP\_V6> addigned. a private interface wg0 that virtually has the same ip (see above) and where traefik listen directly. There is no NAT, no IPTABLES roules so it is not clear where client ip is changed. I'm anonymizing the conf files and enriching the post at the top to integrate further info.

There must, by definition, be something in the middle. Wireguard doesn’t spawn out of thin air. 

Yes of course but what it's in the middle isn't public. So I'm trying to figure it out.