I would second this.
And also, while I don't currently follow any series that is or was deleted, I have seen when browsing user profiles the 'deleted' entries in Reading Lists. I assume leaving a reference in the list is meant for the user to manage their own list and remove the deleted references or something. And I'm enough of a programmer myself to know, it's a difficult enough thing to send notifications to users when a story they follow is deleted ― so they can remove it from their followed stories ― even if this might help 'streamline' the reader lists some. Surely when a story/chapter/whatever is deleted that can be linked, if a notification could be sent to its readers then maybe it would level out in due time?
As an adjunct to this topic, for a "not first person" perusal of a user's reading list, I also do not need to see the deleted stories.