His initial post attracted tens of thousands of likes and a comment thread 18,000-posts long.
The debate has raised questions about the status of unmarried women, specifically, as Li Yinhe, a leading sex researcher put it, "whether or not single women have reproductive rights".
China's coercive population policies discourages single women from having children. Unmarried mothers often can't get critical documents for their offspring, for instance, and are sometimes forced to pay fees.
The policy is driven by twin obsessions of the Chinese state: population control and social stability.
For decades now the Government has controlled the population through marriage, says Li, primarily by limiting most couples to one child.
"The state thinks if it grants a single woman reproductive rights, population control will be messed up," she said.
This helps explain the state's general lack of enthusiasm for reproductive technology of any sort.
But there's more to it. With China's population pyramid shifting, the Government is slowly easing up on the one-child policy, increasing the number of couples - married, heterosexual couples - that are permitted to have a second child.
But single women? No.
This reflects the Communist Party's belief that a "harmonious family" (here defined as a married man and woman and legally registered child) is the bedrock of a "harmonious society", says Leta Hong Fincher, author of Leftover Women: The Resurgence of Gender Inequality in China.
"The prospect of women being able to give birth on their own is very threatening to the moral order," she said.
Which is why Xu's comments made such waves. She is one of a growing number of women who have the financial security to live on their own if they choose, and to travel outside China should they please. Most women don't have those options.
Li says the Government ought to change course, and adopt a more open policy.
"Because of population control, women were not allowed to have more than one child, now if they are not married, they cannot have any," she said. "It's a little too cruel."