Why am I seeing iCal invites to other peoples calendars after updating to Mavericks?

After my upgrade to Mavericks, using iCal 7, I am now seeing many invites that are to calendars I subscribe to (i.e. not my calendars) - even though these calendars are just being shared as "Public" and not ones that I should be able to edit.

Note: Clicking on Accept, etc on these invites does not accept the invite in other people's calendars.