[Update 27 January 2020: I am pleased to announce that, thanks to tireless work by @eol, registrations have been re-enabled. Anything looking like a potential ‘spam bot’ account has been deleted.]
Spam registrations are being made currently on the site at a rate of one every couple of minutes. Members here have rightly complained that user profiles comprising spam adverts are distracting and inappropriate. Pending the development of a technical solution, I have disabled new user registrations. Apologies for any inconvenience.