Unfortunately, because of persistent signups by spam users (probably driven by a script somewhere), I’ve decided to disable the facility to sign up to this site.
Really the only reason for allowing people to sign up in the first place was to in turn limit posting of comments and forums posts to registered users, again to avoid spam.
As a result, turning off sign-up may make it impossible for people to leave comments or use the forum. This is a real shame, but the alternative is just too annoying to police. In the meantime I’ll look into some alternatives. I may re-enable anonymous posting, along with captcha forms, but I fear that doing so will also result in a torrent of spam.