I think you misunderstand communities. Vibrant communities are full of people who share a materially common set of opinions about various things. They engage and interact within that world view.
At the same time people evolve and communities evolve. Sometimes you move away from the community, sometimes they move away from you. Either way, you can end up feeling like an outsider in a group you once considered yourself to be part of the 'in' crowd.
Because a large part of anyone's current point of view is driven by past experience, communities often segment by age but sometimes segment by politics or world events (the mechanism is that people take away different things from the same experience, it "changes" them in different ways, and that puts into further out or closer to other members of the community.
The internet "echo chamber effect" as you call it is defeated by visiting multiple communities and watching and noting the differences. That your favorite 'hang out' on the Internet has become distasteful to you can no more be "fixed" than you can will your favorite eatery or bar to exist for all time.
Things change, people change, places change. Keep moving and an open mind.
Speaking for Reddit, it was an unfortunate consequence of the pseudonymous and point system. As communities got larger, there would be less and less tolerance for discussion and focus would stray towards quick (easily digested) posts.
Although, the counter point is that people in general are less likely to produce discussion. Or, that a lack there of of easily digested posts invokes discussion.
So does the karma/points thing make it an attractive nusiance for trolls? It does seem to encourage participation which is one of the challenges of any community (way more lurkers than speakers)
At the same time people evolve and communities evolve. Sometimes you move away from the community, sometimes they move away from you. Either way, you can end up feeling like an outsider in a group you once considered yourself to be part of the 'in' crowd.
Because a large part of anyone's current point of view is driven by past experience, communities often segment by age but sometimes segment by politics or world events (the mechanism is that people take away different things from the same experience, it "changes" them in different ways, and that puts into further out or closer to other members of the community.
The internet "echo chamber effect" as you call it is defeated by visiting multiple communities and watching and noting the differences. That your favorite 'hang out' on the Internet has become distasteful to you can no more be "fixed" than you can will your favorite eatery or bar to exist for all time.
Things change, people change, places change. Keep moving and an open mind.