As designed Removing Content still lets according Notices in Place

[Marcus]

I create a post
Users get notified for this post
I delete this post
The notices are still in place. They should be removed.

 

[Mike]

If you soft delete content, then any alerts will definitely stay -- the post still exists, you just may not be able to see it. However, the alert does a permission check so you will only see the alert if you can still see the post. (The unread alert count not being exact is an acceptable trade off.)