I did some testing, and apparently one doesn’t get any notification if someone sends you a private message. Not in the web interface and no email notification. No wonder people don’t answer.
Though, I think I got a red dot,or something like that, next to the mailbox symbol, last time I got a message. But maybe I got lucky. Testing between my regular account and a test account generates no such things.
Rather than just deleting an event, I wanted to let the user that created it know the problem and let the user change or delete it. If the user doesn’t see my message, I instead have to look up and send an email, or just delete it without notice.