Calendar apps should let individuals rename shared events for themselves, without renaming the event for all the invitees. If I have coffee with Sally, the same event should be named “Paul coffee” for Sally and “Sally coffee” for me.

Do any calendar clients out there do this? It seems so obvious. Am I just missing it?

I've never seen anything like this. It feels like most calendar apps are designed around the limitations of ics/CalDAV/etc, and don't have any concept of "my view and the shared view are different".

I'd love to have a calendar server that puts me in control like this, integrated with my email so that it picks up on all ics files automatically.