Not sure about the parent poster, but I am here mostly for the comments, and rarely visit the linked content.
Yes there is sometimes an echo chamber here, but it's only for limited topics. It very much has a Silicon Valley feel to it, but @dang and I have gone around on this and he assures us that the readership and comments have broad geographic representation.[1] It's a worldwide echo chamber. :)
Fortunately the echo chamber doesn't exist for most submissions. Most of the discussion on HN is on non-polarizing topics.
So some UK or EU specific topics will appear, be commented upon but then disappear later in the day.
It would be interesting to see what kind of topics are commented on from different places.
What creates an echo chamber is if all the posts are similar or otherwise in agreement with each other. Those threads make for boring reading and I tend to only scan them for less boring content (yes, that means I read the context surrounding greyed-out comments more than the rest). The threads where people discuss various aspects and experiences is what I come here for.
(full disclosure, I mostly read the comments before even opening the article. I only read the article if there's a high-quality comment thread about some details in the article, or if multiple commenters state that it's a great article. And I tend to upvote an article based on the quality of the comments, not just the article itself).