nginx now has ipv6 support! Yay! To have it work on Debian, all you need to do is open up /etc/nginx/sites-available/default and replace:

listen   80;

with

listen [::]:80  default ipv6only=on;

ipv6only=on here is a bit of a lie - it will listen on both ipv4 and ipv6.

Then, in your /etc/nginx/sites-available/* files, add

listen       [::]:80;

just below

listen       80;

so nginx listens on both.