The customer service answer to my "please delete" request, just in case you ever want/need to use this feature. the link to "block this host" is inside the original email containing the link to the event. If you were hoping not to show up as having viewed the invitation, be aware that clicking the link will take you to the invitation, where you will verify that you wish to block the host. So the host will be able to see that you viewed the invitation, but hopefully will not be able to send other invitations to you in the future.
Crossing my fingers that this removes one more annual intrusion. I know it's probably a vain hope, but it feels like another boundary defended.