Hmmm... This poster has noticed an issue on 17th, mailed support and without waiting to see if there's any reply or resolution, decided to blog publicly about it the same day... seems definitely premature, maybe borderline of questionable professionalism. It appears MailChimp has a chat option for support on weekdays for paid users but since this hasn't been used, one would assume the poster is using a free plan - no…
FWIW, MC did respond, saying essentially that there is nothing they are willing to do, and that I need to create a new account. I have written them back asking if I will be able to access my old mailing list from my new account (obviously the answer to that is going to be "no" but I want to get it on the record). They have not responded.