Hello,
We indeed need to document this section of the administration UI, thanks for the reminder!
You can find the login-block information in the metadata attached to a support ticket. For example on CryptPad.fr:
"blockLocation": "https://files.cryptpad.fr/block/oc/SOME_RANDOM_CHARACTERS",
It can be useful if for whatever reason they can't delete their account, we can manually delete that block. Though that wouldn't delete their documents and drive, which could still be a good idea to do so.