HN aggregates, it has no illusions of creating original works. Occasional high-quality reposts are a virtue of HN, and I don't think HN suffers from the same regurgitation issues as film sites. The film websites often come with analysis or reviews of films where the regurgitation lies, whereas Hacker News provides no editorialized comment on the articles, only discussion.

"Echo Chambers" etc... could be merely a distributed version regurgitated content, however I think the HN community tends to self-police groupthink

The comments on HN are quite often regurgitated, especially for the political topics rehashed every week.

Comments are not the main content that HN aggregates. They facilitate discussions around the main content, which are just either links or at best a question.

Reposting the same thing is fine. It helps new people find the content.

Regurgitating a meaninglessly mangled version of something (intentionally or not) on order to plagiarize without getting caught, is terrible pollution.

I'm actually fine with that. I found the article this time, plus it helps to discuss with a new set of people.