My initial concern, based on reading the abstract, is that since this study only looks at Twitter and not Facebook, it isn’t enough evidence to make any conclusions about echo chambers in a general way as so many people get their news from Facebook.

Facebook tends towards people you know in real life, so it’d be closer to the echo chamber that is your immediate social circle, but possibly a bit more open because it doesn’t concentrate your attention as much as you probably do offline, i. e. 50 % with spouse and only seeing your high school buddy every two years.

I guess a lot depends on your job: if you work in healthcare or retail, you‘lo have pretty diverse interactions. Software developer in their home office? Not so much.

Twitter and Facebook are what you make of it.

Reddit popular is a total echo chamber. Almost every sub, outside of focused hobby subs, turn into echo chambers eventually.

The dynamics of reddit, with downvotes totally squelching dissenting opinions and upvotes promoting popular ones, is naturally going to turn into a total echo chamber.

If you haven't touched Reddit in a while - especially if you've been involved in real conversations/work on the same topics in the meantime - it's a bizarre experience to visit various subreddits and see the particular subcultures which have developed. It tends to be very narrow, uninteresting, and annoying. I think most any monolithic community is going to be more or less like this.

It definitely includes hobby subs too. Like, you may find everyone reciting "never do X", even though it's actually correct to do X sometimes, and that's just an oversimplified rule for beginners.

It's why I keep coming back to Twitter, because it only gives me exactly the people I choose to follow, even if I sometimes have to fight the app to keep that default chronological view with no garbage added.