The researchers were analyzing message blocks, where there is explicit feedback from Weibo that your message isn't harmonious enough. Has Weibo has resorted to hell banning messages yet; where the user thinks the message has gone through but is silently repressed by the system from reaching many users? That should be detectable though by using multiple accounts in the experiment.

Yes, you suggest a way that may detect blocks. According to the researcher's website, he is using the search function of weibo to check which words are blocked, that is smart. It seems that weibo are using program and hiring people to do the censorship. There even are rumors saying that those censorship department are settled in WuHan city, and has a team of more than 500 people. Anyway, his research is valuable, and it helps bringing more sunshine to the weibo land.