To be honest I can come across as a cynical jerk, but unlike a lot of the people I see chastising other people in the comments, I'm at times cynical but never intentionally rude. There is a big difference between cynical and just plain rude. Pick any story on the homepage at any given time and people are nitpicking at peoples grammar and arguing something isn't right instead of contributing to the discussion.
Case in point all of this recent discussion about App.net. There appear to be two sides of the fence, one of those sides is hopeful that App.net will be successful and wishing Dalton Caldwell the best and the other side are making assumptions that it's going to fail and that people won't pay to use it, blah blah blah. This is the exact attitude the poster is talking about and I think all of the App.net submissions and comments are a great example of this ridiculous behaviour.
Etiquette aside, don't get me started on the submission quality. It feels like the homepage of HN is part interesting and beneficial submissions and the other half is comprised of articles; "Hating on X programming language", a blog post written by a Svbtle author (mostly Dustin Curtis), a Daring Fireball blog post, TechCrunch news article or submission of a Github repository for something built on-top of a programming language that I don't even know.