:::Just to ramble on a bit, the IP is in the UK, and today is a school day for most secondary schools there, so posting unhappy edits on an early secondary syllabus related topic just before 6pm local time may indicate that the editor was doing homework and grew sufficiently bored to try out the "anyone can edit" thing. Which is slightly intentional I suppose. It's not quite trolling as such (by my definition), since it's entirely possible they had no expectation anyone would ever see the edit or react to it. The welcome with a link to their contributions might have an interesting effect on that possible lack of awareness.