I would like to be able to take control of my data, in line with literally every other legal requirement across the internet.

I believe it's called "The right to be forgotten"

Please give members the choice as to whether or not they want D2JSP to have their data.

You’ve posted over 1,000 times bro, you want to remain anonymous?

Not anonymous - I want to delete my account in full, including all comments/posts/metadata.

I want one million dollars and a lamborghini.

Most will allow deletion of account/personal info.

Not “everything I ever posted”

Right to be forgotten is only enforced in select countries, and the US is not one of them. You may still use the contact form to see if they’re willing to work something out with you: https://forums.d2jsp.org/contact.php