Regarding the first post, you are totally right, when marking attendance to a repeating event it should only affect the specific event instance and not all of them. This will be reported as a bug.
Regarding the visual cue, there currently is an icon top right of events on the weekly and daily views, which shows a green tick if you're attending, a blue question mark if you may be attending or a red cross if you're not attending. There's none on the monthly view, so maybe it would be nice to strike-through the name as your suggest.