Thanks for your reply, there are many ideas that help me to think it through!
First of all: no, I agree that non-verified person should not be able to request an account deletion. However, I am in full possession of my id, password, 2FA, full access to both old and new e-mail boxes as well as to all devices that have ever been used to log into this account. I believe that this is enough to prove that I am the one holding the account.
I believe that I never used LI from any new VPN (I use either professional VPN or no VPN).
As per your last paragraph, I totally agree that it might “reveal” my sensitive data. My idea was the following: if I show myself ready enough and kinda literate about privacy (nothing fancy, just some well-known rights and regulations) I might get them to accept a video call or something similar to confirm my identity. If this case were to be brought to court after all, I believe that my ID data might remain within the jurisdiction of my country instead of be sent to a third party (Persona).
I’d might accept to send my ID with my photo, first and last name (data which they already have and might use to verify my identity) but with all the remaining info being anonymized / blurred. But I believe that Persona filter out blurred out images. And I have to admit, I am kinda afraid to send fake data. Sure, Persona is not a legal representative but a third party, sending them a fake ID isn’t any different to send a fake ID to a buddy but still.