I reached that threshold mostly via submissions, I don't comment that much (but also downvote very rarely). Surely, also submissions may add to the echo chamber, especially if they hit a nerve.

One reason for me to stay here is the diversity (and civility) of the comments, I don't think it's too bad. Another favourite read of mine is Arstechnica, but the comments there don't reach the quality of the comments on HN, imho.