It sort of is, but it benefits a lot from the (virtually) unlimited number of characters you can use. It's possible to express complex and nuanced points on HN, which is impossible on Twitter by the nature of their decision to cap everyone to tiny messages.

The Twitter length limit is a great growth hack because you ensure nobody can excel, so everyone feels they can tweet just as well as anyone else can. But is atrocious if your goal is to promote debate and intelligent discussion. It's a medium explicitly designed to prevent any kind of complex conversation - big surprise how it turns out.

HN has its own set of problems of course: like most discussion forum software it confuses "I disagree with your view" with "I disagree with how you expressed your view", so people routinely downvote well reasoned and polite posts that simply cause them cognitive dissonance or that they find inconveniently true. It'd be better to explicitly separate the two, but I never saw any forums that did so.

But it's at least got the basics right: the screen space is devoted to high density text.