On a Mac, control clicking on a thought in the plex brings up the contextual menu, while command clicking on a thought adds the thought to the selection box. But inside the reports window, control clicking on a thought simultaneously brings up the contextual menu and adds the thought to the selection box, while command clicking just activates the thought. It seems to me the behavior should be the same as in the plex. This behavior is present in PB 5.0 as well as in the most recent beta (22.214.171.124).
OSX 10.5.6, Java SE 6