On both my VPS' of Bitcoin nodes, I have a single eth0 interface with 1 IPv4 and 4 IPv6 addresses.
And my setup on IPv6 was initially "standard". But I thought that causes the problem on IPv6 Bitcoin node connections as the the outgoing packets use different IPv6 address than the IPv6 address used by the incoming packets which Bitcoin node listens to. That is why I made sure that Bitcoin only uses a single IPv6 address for both incoming and outgoing packets. But this turned out to be in fact an issue according to you.
I am not sure what you meant by "permanent" and "temporary" addresses. All IPv4 and IPv6 addresses on my eth0 are all permanent addresses. Perhaps the "temporary" address that you meant is the "link-local addresses".
This becomes more confusing than I expected. Unfortunately, there is no documentation related to this that I can find.
If you configured you IPv6 addresses by hand then your deployment wasn't canonical. The normal, expected way of deploying IPv4 is DHCP; the normal, expected way of deploying IPv6 is DHCP6 or SLAAC.
The temporary and permanent IPv6 addresses are described in RFC 4941
http://tools.ietf.org/html/rfc4941 "Privacy Extensions for Stateless Address Autoconfiguration in IPv6". There's plenty of tutorials available if you find reading RFCs too difficult.
My guess is that your nodes are operating properly, although maybe non-optimal. You probably simply don't understand some wrinkle in the expected network deployment procedures. The IPv6 represents return to the normalcy, auto-configuration is default, like it was in nearly every network protocol stack like DECNET, Novell, AppleTalk, etc. IPv4 was the odd one requiring so much manual settings.
What I would actually recommend is that you rent a Windows VPS for a short term evaluation, just to understand how it should be done. It somewhat pains me to be recommending Windows, but that is the reality: Microsoft did it right while most of Linux distributions screwed up.