The cross-posting problem is specific to Tor Browser, which is Firefox based. But that one was fixed in 0.19.5.
I was actually shocked to recently learn many are using their phones, which often means 3rd party apps (and which would not have any of the stock UI bugs).
One of the big problems social and collaboration platforms is people go to where the people are, like Lemmings, with disregard to principles and ethics. I go to the ethical venues regardless of where the people are. Instead of feeding a harmful network effect, I would rather feed free and open spaces. If I were to contribute to MS Github, I would have to consider myself part of the problem.