People click on threads which are interesting to them, according to their topic. If you're interested in a topic, you most likely view it positively, or as you would put it, you're part of it's echo-chamber. If you then see a positive, reaffirming comment, you'll probably like it.

Doesn't seem that bad to me, especially because I frequently see that the most upvoted reply to the top comment are often contrarian, starting discussions etc.

Echo chamber is such an overused word. In other words, you define that people are part of an echo chamber because you personally don't agree with the majority, which makes you a bit of a contrarian, reactionary hater ;) (exaggerating a bit here)

e.g. - that feeling of having to respond to the person that responded to you, rather than giving the community a chance to respond.

worked for me at least.