Hello again, just to clarify, it was a little confuse for who weren't following the messages we exchanged in private.
Somehow from China, connections to our forums were being intercepted by a third-party server which responded, instead of pages, a non-standard "530" message. The pages were just replaced by 530.
By researching the reason, all led us to believe that the China's censorship filtered our IPs (by accident, or a range of IPs that affected us), intercepting HTTP connections and returning "530" to any page load request. The closest we could find for this code was FTP error 530 which means "not logged in" (
source).
After that, we enabled CloudFlare host accelerator to our forums and websites. This improved forums experience all around the globe, fortunately. Also enabled back access to forums from China.
Not so fortunately though, sometimes CloudFlare triggered a 520 error, mentioned on the post above. So far, we could notice this a couple times from Canada just after implementing the accelerator service, and no longer after a few hours. From China it's been reported to be happening somehow frequently but we are counting that their services, as they log the errors, fixes automatically.
We're currently in touch with CPA1158139 trying to assess the situation from China and hopefully, with the help of the CloudFlare service, bring it to a fully functional state.
We received reports of some failures loading the CSS (which makes the page load, but look strange) from China as well.
The most we try to reproduce the issues from outside China (specially from Canada, Russia and Brazil) we couldn't so far reproduce the issues. So still seems an issue specific to China connections.
I hope this makes clear the state and advances on the issue (originally 530 error while loading pages).