I received a notification for a comment-reply addressed to me, but when I followed the link to the post, the post had been deleted. At this point I figured I just had a stale view of the page, so I refreshed the page. The comment notification was still in my inbox, and the link to the deleted post was still there.
If memory serves, refreshing the page would remove comment notifications for deleted posts. If it's relevant, I first viewed the notification when my ios app alerted me of the comment. Opening the notification lead to a page that said the question was deleted. And opening the page in my browser mentions that it "was removed from Meta Stack Overflow for reasons of moderation."
This notification is also sticking around in my SE network inbox. It stuck around even after syncing my oldest profile.
Is this the intended behavior of notifications? Or am I just misremembering?