Hi John,
I researched this topic on One awhile back (see discussion here) because we wanted to give users a custom project report that displayed current projects owned by them or shared with them, but did NOT include projects shared with them through Inherited Permissions (such as via Portfolio access). The intent of this project report was to give users a drilled-down look at projects they should be focused on vs. the kitchen sink! This was the text mode portion from that discussion that did the trick:
accessRules:isInherited=false
accessRules:isInherited_Mod=eq