I still have the impression that HN discussions are of higher relevance than on e.g. reddit. And a community "being polluted" suggests that there are "pure" me

I still have the impression that HN discussions are of higher relevance than on e.g. reddit. And a community "being polluted" suggests that there are "pure" members and "dirt" members -- I don't think that's a helpful angle to discuss a possible decline in average relevance of topics and comments.