I'm thinking that things are getting to the point of maturity that it'd make sense to have a general rule about this.
Something like:
You're expected to do a little research to see if your new community is very closely aligned with an existing one, and if so, provide at least some statement as to why you're making yours or what's different about it.
It's not to prevent people from making their own communities at all, it's just that it actually helps clarify the promotion of a new community while also helping the community ecosystem.