Just messing around to see what I could bust, and this happened: Right clicked on my commander whilst he was selected (my only unit at that point), and having caps on revealed that he could assist himself. All dirty jokes aside, this could be rather annoying, as anything you shift-click doesn't get done after the assist self happens. Since shift-rightclick can be used to path up move commands....... I noticed the tracker bug listing for this was closed (http://pa.lennardf1989.com/Tracker/index.php?do=details&task_id=1052), and listed another potential issue with multiple fabs, and setting assist orders. EDIT: added screenshot!
Re: [Closed Bug? Feature Incomplete?] Assist Self stops work Commanders really are brutally efficient.