At the moment, I am having some difficulty finding a case where clicking on "pin" changes the behaviour. It seems that whether or not "pin" is checked, the same thing happens, i.e.
1) details of the newly selected node are displayed, without redrawing the box, as long as the newly selected node isn't a cross-link
2) details of the newly selected node are displayed, and the box is redrawn (navigation occurs), whenever the newly selected node is a cross-link.

Example of the behaviour I would tend to expect from the pin check-box:
Go to http://debategraph.org/Stream.aspx?nid=2768&iv=04
With pin on, a click on any of the cross-links should display the cross-links details without navigating to it
With pin off, a click on a cross-link should display its details AND navigate to it.