That was absolutely NOT the case - I’ve only ever had one server, but I have (then and now) run unofficial apps and all this happened many, many, many PMS versions ago. Regardless - I will NEVER try to put the same TV Show in two different libraries for as long as I live. That experience has scarred me for life.

I should have said directoryA/TV and directoryB/TV… either way, I can see the potential for stickiness.
A quick wrap up for clarity:
AmazingRando is 100% correct. Sorry about that Juice but you can have the same TV show in multiple libraries. I am now doing so with great success.
The “random” deletions I experienced were anything but. They were caused by me setting deletion parameters in a scheduled DVR recording. These settings, as Rando astutely points out, apply to all occurrences of the show, regardless of library and therefore regardless of source (ripped disks or DVR recordings). And they stick even if you delete the schedule.
So rejoice fellow Plexers! You can record new seasons without fear of wrecking your back catalog.
Thanks to all for the valuable dialogue.
Well there’s my feelgood moment for the day!