@Saket There's a very good article that summarizes it (+ surrounding research) well, but unfortunately it is in Dutch: https://www.nrc.nl/nieuws/2022/11/04/het-is-de-sfeer-niet-de-bubbel-a4147353

A *very* concise translation/explanation would be:
- People always tend look for like-minded people to some degree, as a normal social mechanism, to reduce social friction (and this is not a bad thing)
- But they will also venture outside their own group to learn other perspectives
- Understanding for other groups can be actively improved by bringing them together in cooperative scenarios...
- ... *but*, when people are brought together in *combative* scenarios (eg. forced together), it just increases polarization, and actually makes people close up and *not* venture outside their own group

The summary of the summary: people naturally compensate for the risks of an echo chamber, but they stop doing so when you take away their agency and try to force them to interact with others, and it *causes* the 'bubble' problem.

So it's not that 'echo chambers' don't exist as a concept, or that they can't be harmful, but more that the (right-wing) hypothesis of "people must be pulled out of them forcibly" is completely false and the opposite is true.

It's not without reason that right-wingers constantly talk about echo chambers whereas leftists usually don't. It's essentially just a disguised way of saying "we want to force others to listen to us".