It's because such comments break the HN guidelines by treading into classic flamewar territory with nothing genuinely new to say. This ruins threads and degrades the site. A few people get all excited (perhaps 0.1% because they've never seen this before and 99.9% who just love repeating it) while the rest of us keel over from tedium. Since HN's mandate is to gratify intellectual curiosity, that violates it.