It seems weird that HR would go out of their way to tell you you are permanently blackballed, when they have enough trouble responding to people who they are open to hiring in the future, and since it is such an obvious embarrassment and legal risk to have a policy of telling candidates they are blackballed.
It might have been easier for the interviewer to fill out his evaluation form with "Did not answer the provided questions" (or similar) rather than "Not interested in working for us".
HR might not have got the full story.
Still weird that they'd make a point of saying he wasn't welcome to come back and try again.
