you are correct on the invite/clan play question. Ventrilo is an application for windows/mac/linux and Andriod which does voice communication similar to how the PS3 handles voice chat. The only difference is you don't get any CoD whiners or trash talk since it's just us... ohh, and it works. Once you download the application, you can set it up by clicking this link/going to this url: ventrilo://jonahan52.servebeer.com:3784/servername=RedditVent
This should get you onto the voice chat server. Once you're in, you can click on the chat room you want to join. (I only see two at the time of writing, Killzone & reddit)
Enjoy the game, it really is fun when you clan up!
As soon as I started playing MP I knew this wasn't true. It was immediately obvious that this was true:
http://www.ign.com/articles/2014/03/06/killzone-shadow-fall-dev-addresses-multiplayer-resolution