All these cases are for actual criminal acts (or accusation of it) not for something as arbitrary and laughable as "discussing Bitcoin on a forum". Not to mention that Bitcoin is not banned in China in the way you think it is; mining bitcoin, CEXes that were laundering money with 0 fee, ICOs, etc. are banned.

Besides, there is a higher chance that US arrests theymos like they did BurtW than there is China arresting the Chinese board's moderator.