Suggestion regarding the Spam iCal adverts masquerading as invites
I have started receiving these, as so many folk worldwide have. I have used the workaround and managed to delete the invites without notifying the perpetrator.
My suggestion, since Apple Support can be hard to get hold of, is to use Twitter to @applesupport to express the concern over the problem. https://twitter.com/AppleSupport is their twitter account.
I apologise if this post is out of scope. The problem is becoming so widespread there is a danger of its flooding these forums in iCloud and iCal threads.
macOS Sierra (10.12.1)