The thing that surprised me most is how publicly abrasive people can be when they're using their Real Names with real photos and real descriptions of their children and pets just a click away, talking to people who live just down the street.
There's a big hubbub in my 'hood about some homeowners who want to rebuild our community pool, a multi-million dollar project. Vast majority of the neighbourhood doesn't care one way or the other, but they don't want their HOA fees to increase.
Had it not been for Nextdoor, the loud minority would have quietly passed the bill and started construction because nobody attends the community meetings or bothered to vote. Except, Nextdoor started taking off in our area just at the right time and a bunch of people flipped out when they found out about this through various threads on Nextdoor.
There was namecalling, sarcasm, pedantry, even classic trolling (people taking positions that they clearly don't care about just to upset the original poster). Almost Youtube-comment level stuff. Even weirder, most of our neighbours are middle-aged or older. They didn't grow up with this kind of online behaviour and had trouble recognizing it.
Clearly the behaviour of these people is not Nextdoor's fault. I am grateful that Nextdoor is there partly for passively observing the drama in my community and partly for actually feeling like I'm getting to know the people I run into when I walk my dog.
Coming away from working at Google during the peak of the Real Name controversy, it's weird to see the benefit premise explicitly shaken, if not refuted.