Accepting an event invitation makes the event a recurrence-exception

[kesselb]

1. Alice invites Bob to an event (takes place once a week and will end after 20 occurences)
2. Bob accepts the invitation
3. The attendence status is updated for Alice
4. It's not possible to modify the recurrence settings now

I find it weird that accepting the event invitation by an attendee does change to be a recurrence-exception even if the date and time is still the same.