Accounts have to start posting somewhen.
Moderators don't have the capacity (and fairly, it is impossible) to check if they are bots or humans.
There are no good solutions, there are hundreds of thousands of intelligences out there, trained millions of hours on how to scam humans, capable of spitting out text tirelessly and shamelessly, and there will be only more of them, tens, hundreds, thousands times more.
Comments should be allowed from day one, but submissions should require some experience and karma.