It's not, but when the comments read like they're from impressed third parties, it smells a bit. Imagine if coauthors of a book posted reviews on Amazon along the lines of "Wow! This book is amazing and has a great design" without disclosing their authorship, it looks weird. Instead, they should have gone with something more natural like "Just wanted to say I was involved with one of the slides in this project and I think it's turned out great!" I doubt such comments would have been voted down to oblivion.

If you haven't been around here, you may not have noticed that there aren't a whole lot of "Me too" or "First post!" type of comments.

Some of the comments on HN could pass for short essays with subsequent panel discussions. That's why we read it.