According to the delete-account help, users are required to put the text "please delete me" in their profile's "about me" text. But a suspended user can not edit their profile, so they are unable to follow the required process.
Often enough, a suspended user feels so vengeful that they have a burning desire to rage quit by deleting their account, but alas they can not while suspended.
It would be good to support such users to fulfil their desires by providing a rage quit link that appears only for suspended users:
By the way, there is some basis for this question. I had a request for "how to delete my account" from a recently-suspended user.