They didn't care/enforce it during the whole anime_titties/worldpolitics shenanigans, so either new or enforced when they feel like it. Centralised control sure is great.
Jannies have never been good at relating to people, and reddit admins are like the jannies' janny. Ban-happiness is inevitable.
Forums are an interesting model for real life human social structures. If you operate your social structural group in such a way that the only way of meting out punishment is exclusion, eventually you can create an outgroup that becomes a threatening competitor.
When your containment board is another website, you lose.