Probably /r/themotte, a place where people who think of themselves as hyper-rational use polite language to veil their abhorrent opinions.
It sounds like we’re aligned that that subreddit is in danger because of its political opinions, not its communication style? Which is exactly counter to Yishan’s claims.
I just looked at that subreddit for the first time. It seems completely harmless. I didn't read a single thing that was controversial. It does probably contain some of the longest and most structured comments I've seen on reddit. But I'd be surprised if this was the subreddit the original poster was talking about (unless all of the "good stuff" was already banned).