I couldn't agree with you more on the attitude of SO, as they can be pretty horrible if they feel it. Before discovering this kick ass site, I would / could be found in the Experts Exchange community, and I learned tons about dev work through asking/answering questions on there, and most folks are amazingly kind, but there's always a chance you'll run into an a-hole.
I also think one of the bigger difference is HashNode doesn't really focus on "gamification" of the site (such as getting points) or badges or whatever, and they focus more on general info rather than specific Q&A scenarios.
To summarize, I think HN is more focused on community and general overall discussions on whatever technology, while other forums are for specific topics.