Employees, on the other hand, tend not to have much skin in the game, so they're a little more free with their criticism of things that they see. I bet you could put together an interesting chart by running a poll for "where do you work" and graphing negative comments elsewhere on the site by whether a given user answered "for myself" vs "for [company x]".
So yeah, there are still plenty of supportive, encouraging entrepreneurial folk here. But there's also an ever growing peanut gallery. Try to ignore them. They don't mean any harm.
I've been around for 5+ years here I guess and this is my explanation for it as well. I'd also add that such negativity is inevitable for some people - they visit HN 20x a day, they want to contribute in some way, but no one has made a post today that they can "show off" with an answer. In the end, they reply with a silly/off-the-cuff/disresectful/snide/etc answer just b/c they have this need to "participate in the community". HN is reddit-like for many people, myself included, in that way. I'm not immune to it either.
Don't take this comment as negative.
It would be nice if people learned some rhetorical skills to communicate better. But that's a separate issue. As it is, it is on you to interpret the comments in a way that will help you improve. Learn from the helpful suggestions and ignore the unhelpful. Try out, or at least think about, the div styles comment. See if it really is an improvement. If it is, then you just learned something new. If not, then you learned something not to do in the future.
Even the extremely negative comments are usually written in good faith here. Minor incremental improvements such as div styles will make the world a better place. (It sounds like a stupid statement to make, but hackers do believe in better software and its ability to make a difference.)