I think the point of the article is that you can make this happen even without an app. And I believe the previous poster is trying to make the point that an app will create an low effort impersonal engagement that brings out the worst in people (essentially all these apps will end up as nextdoor). Why not invite the next neighbour you meet for a coffee, or do what the guys in the article have been doing and take a camping chair and sit in front of the building with a coffee on Saturday morning?