Your comment seems to imply that posting a link to a thread elsewhere in an attempt to attract sympathetic commenters is a legitimate strategy to "open a debate". On Wikipedia, such commenters are sometimes derisively referred to as meatpuppets; although they may not technically be sockpuppets, the value and effect does not differ significantly, either practically, or, in my view, ethically. Even HN agrees with this in at least one context: it is agreed among almost all members, and, as far as I know, moderators, both past and present, that posting a link to a thread with the purpose of attracting users to take some binary action on the thread (usually upvoting, but sometimes downvoting or flagging) is bad and wrong.

Why should mass commenting be different?

I think an analogy might be drawn to corporate representatives. If they want to advertise and market their products, that may be acceptable, if they are otherwise contributing to the community, outside of their narrow product. If they only post links to their website, they will be banned with great haste. Similarly, if pro-China users want to legitimately contribute to the discussion, they should be free to do so as legitimate members, participating in all elements of the site, not only via pro-China comments.