I guess my approach is aimed more toward casual acquaintances, where you might not know the people on your street very well at all, let alone have their phone number. (but I might be misunderstanding how whatsapp groups work).
Guess it's double-edged though, if you don't confirm a person's exact residence then anyone could read the locality's discussions ... tricky.
Is there something inherently wrong with a random person signing up to a particular neighbourhood's group chat? These aren't exactly going to be super-private conversations if they're with everyone on your street ... and I want to encourage community building ... not necessarily GATED-community building. The end goal is world harmony, not several billion factions.