This was an upgrade from 2.7 Stable to 2.8 Beta 4.
Update: There was a broken plugin which allowed “following” people that added it’s own notifications to stock (from Pavilondev), and it malfunctioned after the update until I updated it to reflect upstream (because we had a private repo for the 2.7 version we forgot about). Scary how Shadow IT spreads.
I would delete this post… but can’t, site admin required.