I'll need to choose an openid provider now that WordPress is being deprecated, and I suspect some providers are blocked in China. I don't expect to visit China very often, but I may want to ask questions on Stack Exchange (especially Travel.SE) while I'm there.
None. If you're in China, you may experience problems using many parts of our site including the login system. As someone who works in the support desk, we've had reports of the entire site being completely unusable from China in some instances because a variety of stuff gets blocked:
- jQuery, reCaptcha, and other Google-hosted utilities (almost always)
- Our in-house OpenID system (frequently)
- Our Stack Auth system which most of our login system runs off of (somewhat frequently)
- Our content delivery network (less frequently)
So, even a lot of our stuff gets blocked on occasion, which can prevent any provider you use from working properly. If you're planning to do anything more than just browsing the site from China, you may not have the greatest of luck if you're not running your requests through a VPN.