This is SE's modus operandi, protest their choices around AI training, policies, etc., by deleting your content and you'll get your account locked and your posts reinstated because you're "hurting the community" and that is more important than your (now non-exclusive) right to your own words (and by non-exclusive, I mean SE's wishes about what to do with your own words matters more than your wishes).

> This is SE's modus operandi, protest their choices around AI training

All of StackOverflow is already scraped and archived, so this is not a good argument, as you are actually just hurting StackOverflow while helping AI companies

Maybe my goal was to hurt SO in protest of their decisions?

Just like those who edited every Reddit comment to a blank string before deleting them all.

My account was locked for deleting my own comments. I sent them a GDPR request to delete my comments. They ignored it. I posted on meta asking if they followed GDPR. It was deleted and I was banned from meta.

Actually, I don't think this is covered by GDPR, but if you are European (which is implied by the fact you invoke GPPR) you can and should file a GDPR complaint to your local DPA.