The summary is this... if people share their calendars with me and I invite them to a meeting, then only the first person to accept the invite gets in... the rest appear to decline the invite.
Here's a reproducible scenario to expose this issue.
There are three people: Alice, Bob, and Carlos.
To reduce the number of variables, everyone signs out of iCloud on their macs and uses only the web interface to iCloud.
Each person creates a new calendar that they share with the other two via iCloud's "Calendar Sharing / Private Calendar". These calendars are shared as "View Only".
Alice now creates an event "Event1" on her calendar and adds Bob and Carlos as invitees.
Bob gets a notification about "Event1" and accepts the invite for the event.
Issue #1: I expect that both Alice and Bob will both see "Event1" on each other's calendar. Actually, Bob sees two events (one on his calendar and one on Alice's). Alice now sees only one event... and it's on Bob's calendar. When Alice turns off Bob's calendar, the event goes away entirely!
Now Carlos sees his notification about "Event1" and accepts.
Issue #2: I expect that (at least) Alice and Carlos will both see "Event1" on each other's calendar. Actually, Alice is notified that Carlos has declined! Carlos appears to have declined on his calendar too. And while the event continues to show the maybe/decline/accept links, Carlos can not accept the invite.
It would seem to me that this is a fairly common scenario. These could be three family members, three friends, or three colleagues at work. I'm having a really hard time believing that this scenario doesn't work, am I missing something or is this really as broken as it seems?