The website nextdoor.com invited me to join. Then they deleted my post about a local Black Lives Matter protest. Here’s what I wrote. I’m 49, and I’ve lived in the Squirrel Hill neighborhood of Pittsburgh, Pennsylvania, for my entire life.Technically, the neighborhood is divided into two sections, Squirrel Hill North, and Squirrel Hill South.I live in Squirrel Hill South.But realistically, most people never make the distinction between North and South. I myself had lived here for decades before I even became aware of it.Anyway, the website nextdoor.com invited me to join. Then they deleted all three threads that I started.In my...