Yesterday, I randomly picked a sector (Arta C K2) where myself (Serco) and another Serco player could practice a little PVP. Turns out neither of us could damage each other..

I requested a UIT player come check, and we could both damage that player. and He could damage us.

Same nation (assuming good standing) cannot damage eachother in capital systems unless duelling. In other news, you're an idiot.