BS. Straight BS. Writing "SSSS" on the boarding pass in pen doesn't bat an eye anymore. SSSS data is hard-coded into the boarding pass barcode, so it flags at the gate.

Now, that's not to say a hyper-vigilant GA wouldn't see SSSS scrawled on a boarding pass and call the hyper-vigilant TSA over, who would then g-rape the victim anyway, but SSSS in pen isn't the indicator these days.

Also, I'm calling BS on that story. Reddit's full of self-made heroes who never actually did what they claim to have.