This really needs to be fixed. Especially when the response rate is a metric for account evaluation.
I reported this often and just for the record, I contact CS again.
When I receive a message from a blocked user, I have to unblock him to answer his message in order to keep my response rate up.
However, even when I do this, I now see in my analytics a red exclamation mark telling me that my response rate is only 80%! I always respond within half an hour though.
I only can speek for myself, but if I will be demoted because of a bug in the system, I will leave Fiverr for what it is and never do any gig again.