What actually happened is that certain posts on the trans community were getting downvotes (thought to be caused by brigadiers), so admins started going through the downvotes on certain posts and banning anyone who downvotes them.

I don’t believe it was ever automatic, but downvoting a post in the trans community (or, sometimes, announcement posts on other communities regarding trans matters) could always earn that person a ban. Which is kind of bad if, say, they’re downvoting an announcement post about how downvoting posts on the trans community can get you banned because they disagree with it, and basically being told “you wouldn’t disagree with this obviously shitty idea unless you were a transphobe, BANNED”.

Since they had open account creation, permanent account banning was seen more as a “slap on the wrist” by the admins, who banned people for basically any infraction. In reality the trolls would just make a new account and the only people it would really affect are the good-faith users who made one post that ran afoul of an overzealous moderator.