The new silent majority: People who don't tweet
I was talking about this to friends the other day. I hypothesised this might happen in a paper (apologies, not in English, and not hosted online, I think, anymore) 15 years ago - with the basis of hypothesis being that algorithms that are optimised towards the wrong objective can easily form echo chambers that amplify a certain attitude - but to a dip in/dip out user it looks like a consensus forming - because humans are not good at perceiving difference in problems past a certain scale.What I couldn't imagine back then is that Twitter is going to be the main platform (I was using a nascent FB and early 00's bulletin boards as the examples of the system). And Twitter is absolutely bonkers in terms of how it polarizes opinion. If I didn't know any better, I would think that it was specifically designed to achieve this purpose. If I needed to design a system that polarizes opinion more than Twitter, I would be hard pressed to do it better.1. The 160/240 character limit forces you to reduce topics to their most impactful tenets - which strips out all of the nuance and grounds you into an extreme position. For the one expressing the opinion - it will always look more benign than for the one reading it, because the writer can't fully strip it's perception through bias of known context. 
2. The users have "gotten around that" by starting threads - and Twitter has started optimising the feed to show threaded views - but threads are not generated "at once" (there are tools for that, but most users don't use them). They are generated post by post - and in a fairly complex topic (such as, oh I don't know, the war in Ukraine) - this will mean >10 tweets as part of the thread. Each of those tweets is replyable and because you can like parts rather than the whole thread - it will show in people's feeds piecewise -> which will create discussions on parts of the point, not the full context. 
3. In turn - these piecewise reactions are forming a base for someone else's reaction, where you've gone even further into the rabbit hole. By this point - an argument has already started - and because the 240 char limit doesn't allow for nuance - the argument looks like a black and white argument - as there are no points that are in the "grey zone" that a reader from the side could connect between the opposing sides and perceive any hope of consensus. 
4. Users from the outside see it as B&W - so they enter with B&W assumptions in - and assume an aggressive tone - completely derailing any hope to avoid creation of opposing echo chambers.I can see how they got there - and I can see the choices they made - 160 characters was a good choice for user engagement and revenue - as the flywheel will allow for more ad insertions - and if you optimise for quick reactions - your algorithm is going to take you into a zone where people don't read entire threads - because the algo isn't rewarded for people idling about and not reacting/answering. In terms of what it's doing to public opinion - it should be a textbook example of how growth-oriented product design - when not evaluated hollistically, can create unwanted social effects.EDIT: Forgot to link to original point of the article /facepalm. The reason why it's never going to achieve higher penetration - in my view - is that a lot of people get adverse emotional reactions from how the algorithm works - so you end up having people who have to be there (media) - and people who are quite comfortable with emotionally loaded engagement on social networks - which amplifies all of the functions stated above. And those people are, fortunately, in a minority. However, the fact that people don't tweet, doesn't mean that people don't read the tweets - as twitter is public without an account and major news outlets usually link to twitter threads. This drastically amplifies the reach of the distorted echo-chamber battles - which makes the overall effect on public opinion even worse.I mean it's perfect in how horrible it is.