It helps that the community is smaller and we've had the occasional meta thread discussing rules & phenomenons, with moderators and active posters alike present. We also have a somewhat tight knit community of active participants & mods on IRC. I think this makes the whole thing more human.
There are other factors, for example downvoting because you disagree isn't seen as a valid reason for downvotes on Lobsters. In fact, when you downvote, you must specify a reason (there's a list of choices). Of course people can abuse the system, but I think it sort of encourages people to go down the right path.
The invite system probably helps keep worst of the worst out.
Tags help people ignore the topics they find frustrating.
Speaking of tags, all stories must be tagged and if you can't find an appropriate tag, the story most likely doesn't belong.
We've been trying to focus on purely technical content (and by that I mean really technical and not non-technical stories that are somehow related to technology) with some art, while avoiding politics, inactionable news, opinion pieces and the like. To be fair, as the community has grown larger, it seems like we've been slipping more and more from this ideal and opinion pieces about "practices" (that's a tag) and "culture" (yeah...) have gotten annoyingly common. We can still filter out those tags.
As for getting an account... I think there's something written about that on the site.