I have somehow again added my entire 2-non-vocal playlist to itself. Once again, I am scrolling through a list of duplicates, control-clicking on every other one, then deleting them.
This is not a great way to spend my time.
Even granting that I’m somehow uniquely stupid or careless, I think it’s a UX bug to let even losers like me shoot themselves in the foot so easily. (See closed Massive duplication of playlist entries suddenly appears - #7 by Brian_Marick) for UX analysis.