Who cares about planetary scale? Back when your networking reach was largely limited by the size of your area code, local BBSes had user verification and were incredibly popular.

Most platforms for the last decade have used phone numbers for real-human detection. Facebook is well known to quickly lock new signups' accounts until they give a phone number. Obviously that can be gamed by some people in some places, but all countries on earth have mobile phones now and purchase of a SIM card often requires showing ID to authorities.