I find it odd that there was never an announcement. Every month or so, I’d try to sign back up, but was met with the same error. I’d then come here and look for the official announcement or discussion. It’s strange that it happened without the knowledge of people who’ve been here for many years.
Without breaking anonymity, the mod that was helpful and reactivated my old account for me told me that it was Ben who closed sign-up for new users due to some abusive behavior from a former user.
It would be nice, however, if an official announcement were made.