I bet that this was also the reason why google searches came up with empty results.
Well since this mystery is solved.... how about just always show the 'base' event? Repetitive events are only clones of the first one created, Once you have earmarked these you'll be able to also always show a base event with instances from the past no? If one of these instances is edited, then it becomes a base event itself, no longer part of all instances.
Makes me wonder, is it possible to edit events from the past that are ended? I hope they aren't so history of events is ensured, I haven't tried this though.