Earlier quoted context omitted.
It looks like what they are doing are obfuscating with CSS. See for example: http://www.quora.com/Bayesian-Inference/How-do-Bayesian-algo... The answers are in a span with class "blurred_answer", which has css styles: "color: transparent; text-shadow: 0 0 7px #777". Which in effect makes the text completely unreadable to humans. This is just one step above "color: #fff; background-color: #fff". Scummy.
Unreadable to humans with sight. Screen readers don't care! :-)
Source: http://nerdr.com/see-quora-answers-without-signing-up/