I'd like to add, in a slight variation of what you've said, that it would be better to say "GK is about roleplaying in a medieval context" than that is't plainly about roleplaying. As you pointed out, roleplaying is almost everything, specially in the internet, but most important it's a quite expandable phrase. The problem is that most players "roleplay" pkers and scammers, and as such let a bit too much of their real-life character shine through
.
Besides, Kingdom members don't have to rp - but they're encouraged to do so, and higher ranks are to be a matter of roleplaying, not power or level, at least that's my approach.