Ok I got it. In fact, I modified the settings.php file from GS so I could use a simple slash (/) in the back end setting page instead of a full url, and this plugin uses "relatives links as absolutes links" (weird). So it's ok for now, the comments work as it should, I just have to find a way to visit my site from local network AND from Internet at the same time (if I use my dynamic IP on local network, it redirects me to my internet box home page).
Thanks to Cumbe anyway, and keep going with your great work!
Thanks to Cumbe anyway, and keep going with your great work!