GitHub User: darph
$ sudo vim /etc/nginx/sites-enabled/default
On line 22 (I think) you will see a line that says listen [::]:80 default_server; - comment that one out. then :wq [enter] to save and close.
listen [::]:80 default_server;
Then try again: sudo service nginx start. Or just don't worry about it, as the file will be deleted later in the tutorial.
sudo service nginx start