I've understood that companies are allowed to retain data that they need for legal reasons even if you do a GDPR delete request – and by posting on Stack Overfl

I've understood that companies are allowed to retain data that they need for legal reasons even if you do a GDPR delete request – and by posting on Stack Overflow you've granted them a perpetual, unrevokable license to your posts under the condition that they attribute the work to you. Sounds legally complicated to say the least.