So, Quora's rationale for blocking the Internet Archive is that Quora can't go back and automatically rewrite history whenever one of its users wants to.
It's the same rationale that EU courts used to make Google remove search results on user's request. Many people think like that apparently. It had defenders even here.
Yes, to me this sounds less like a business model issue and more like Quora has implemented a "right to be forgotten". I wonder if this is related to a kind of "leaker" culture on Quora where people answer questions about companies where they work ...and later may change their minds about it.
A rational could be perfectly legitimate for deciding to not give someone information, but horribly inappropriate for forcing someone else to not give out information.
It's the same rationale that EU courts used to make Google remove search results on user's request. Many people think like that apparently. It had defenders even here.