I'm not sure echo chambers are bad - I like the "warrens and plazas" idea. If ideas really are a market - or more relevantly, policy is a market - we'd never buy anything if we only had half-baked prototypes to choose from.
That said, twitter really makes me appreciate traditional politics.
Party states in their manifesto they value x, y, z Party representative does something that is consistent, or not, with that (individuals get to decide this, even if the media get to present "an angle").
Some "undesirable group" (Neo-nazis, tankies, etc) may vote for that party, but they don't control the message. Or if they do, the party leader has failed.
Twitter politics, by contrast, is built on the fundamental attribution error. If you don't take the most charitable interpretation of my side, and the worst interpretation of theirs, you're my enemy.
What reddit, twitter even youtube get wrong is that mixed up and down votes might mean very engaging but it does not mean good wholesome healthy content, infact it definitely means the opposite. If you just amplify engagement as they do today it might bring more clicks but it hurts society and builds extremists.
That's what radicalizes people. That, and the easy ability to mob folks who don't toe the line on whatever issue. The most disgusting takes on both sides are amplified, not blocked. And even when blocked, still screen-capped. You see the most unreasonable perspectives amplified but the broad middle folk, or those who have legitimate points, either driven off the platform or who just aren't amplified.
EDIT:I know this is usually frowned upon on HN, but I must ask: Why the downvotes?