I was giving a talk about Python at a club in school and I wouldn't be able to have everyone install an IDE or Python on their computers at the moment. So in the planning phase a fellow club member suggested Repl.it, so that they could run and test the commands we showed. This was a few months ago and it didn't have the multiplayer feature then. I found myself using it recently because I wanted to help a friend with a program idea that was unrelated to the class we were in, I remembered Repl.it and it turned out to have 'multiplayer' in beta, making it easier to talk in class without repeatedly chatting though inline comments.