It usually relies on honesty.
If the vast majority of users is honest (which I would assume is the case in communities like this, because what big interest would men have in impersonating a woman just for answering to women’s topics) then you can have rules that you cannot really enforce. And you still benefit from them, I think there’s a lot less men posting with that rule than without it.
Nach 2-3 Klicks habe ich das hier gefunden. Ist das nicht schon das, wonach Du suchst? Ausfüllen und per Email schicken. Zu meiner Überraschung sogar mit PGP möglich.