But what of trolling then, a sort of counter reaction to the echo chamber where large outliers enter the room and disturb the equilibrium?

For my part I think it's asynchronous written debates that are the source of these problems, so even earlier than facebook.

On a large massive forums, people write for themselves, not the others, and barely read the discussion. Oral debates or written rendering of them, had the advantage to be slow, less variate, and adaptative to a single argumentative line.

Nowadays when you discuss an issue online, everyone starts new train of thought to escape adaptation, and care little about an audience they d need to seduce or convince.

I suppose I just did the same anyway, you can reply but I wont read :)

I think this is partially correct. People write for themselves, but they also write for an audience. The latter is a problem because they can essentially ignore whatever they are responding to as long as triggers n upvote. This disincentivizes honest and productive dialog in favor of nitpicking, gotchas, or simple ridicule.

The former is like a bunch of drunk grandpas mumbling to themselves in a room, the latter is like a self interested orator playing to a crowd. Asynchronous written debate can be the one of the best forms of communication. Think about Jefferson’s letters or other famous correspondence. The incentives are just wrong on boards with ranking and voting

Trolling pushes people further into their echo chambers. It isn't intended to encourage a wider world view, it's intended to hurt. It just convinces people that they're already on the right side.