Now, longtime China-based journalist Mark Kitto says he knows "the true story." He says his source is "someone with access to the top level of the Chinese governing apparatus."
According to Kitto's story, Xi was hit in the back with a chair hurled during a contentious meeting of "the red second generation." These meetings of the Communist Party old guard's elite and now-adult children, which includes Xi, come with a lot of baggage. Old rivalries, petty squabbles, and apparently fights that include flying chairs. Here's Kitto:
The meeting turned violent. They went at it hammer and sickle. Xi Jinping tried to calm them down. He put himself physically in the crossfire and unwittingly into the path of a chair as it was thrown across the room. It hit him in the back, injuring him. Hence the absence, and the silence, and the rumours.
It's a plausible story, but given its single anonymous source, probably best taken as an interesting but not yet verified account.
Kitto argues that this was a lost public-relations opportunity for the party, which could have used the story to point out that Xi has the "courage to quell the squabbling about personal histories and vested interests." It's a common perspective among Western "China bulls" that China's government is actually better than it seems and that its failures often come down to public relations. There's some truth to this, but in this case it's hard to see how rich, old elites fighting in secret meetings would boost popular attitudes toward the party.