There are multiple Vigilant Citizens with large audiences. At least 3 to my knowledge. They've been around for like a decade, if not more.
This one. Another whose Christian and a 3rd on whose actually Muslim. Both are on youtube iirc.
Granted, this VC doesn't have a large audience, but he used to. You used to find mentions of these forums seemingly everywhere. No longer.
How do I delete my account?
Ask VC. If he feels like it, he can ax you. Otherwise, it's not possible.
I don't know why you'd want to anyway. Just stop using the platform. It might be fun to drop in 10 years from now, read your old posts and see what you've once said. Assuming these boards don't get nuked again like they did in 2017.
I ran across some posts I made on Reddit in like 2013 when i realized my old account still existed. Its kinda wild the topics and convos i used to engage in.