But I still received a notification for it in my global inbox a while later:
This has been happening over the past few weeks randomly. Not commonly, but not rarely either.
Mozilla/5.0 (X11; Linux x86_64; rv:46.0) Gecko/20100101 Firefox/46.0. No extensions or userscripts which interfere with the page DOM.
I hope the red free-hand marks are aesthetic enough to give me lots of upvotes.