I mean if you're not using a VPN and don't realize you need to set your device to refuse all connections without it so you don't have a whoopsie, that's kind of on you.
But since Kengle wants users who aren't KF rapefugees, he should disable requiring new users to input a birthday during account creation since they might not realize that's going to be available on their profile and they may input their real one.
"But I have to make sure no minors are signing up"
So put a tiny notice at the bottom of the page that says you must be 18+ or discontinue use of this site. Bam, indemnified from prosecution and the unicorn you seek won't have a key data point doxed out of the gate