In Quora's case the text blurring applies both to search engines and users. I've visited the site as the googlebot user agent and it is exactly the same as what non-logged in users see. They also aren't doing any tricks to hide the full response in the HTML.
Also FYI, most major search engines have "secret" IPs from which they crawl websites using normal user agents (ex: Chrome, Firefox, etc). They then compare the results to the results from their main crawlers to detect the type of cloaking you referred to.