Thanks ChuckPA for putting together a detailed post with screenshots and examples. I appreciate it, though unfortunately it does not address the issue I am describing. My explanation may not have been entirely clear.
What I am facing is a situation where I had a working library, utilising .plexignore in my TV Series root and all was well. Plex crashed and I forced a restart. Upon restart, Plex started adding all that material listed in my .plexignore 
I think the problem comes back to ye olde Plex Dance™. Once the episode files are in Plex, it does not want to let go of them.
My solution was to do the Plex Dance™ using my .plexignore file as input for automation and to delete the offending listings through Plex. Upon moving the material back, Plex has not re-added them. 
This is, however, an incomplete solution because when doing the Plex Dance™ according to OttoKerner, it is a feature to not remove material from Plex, even when doing the Plex Dance™. There are some files that should be ignored but are still attached to a Season as a duplicate file version.
Any suggestion other than “simply delete the library as a whole and re-create it” would be appreciated.
