Obscuring content to non-bot users is still cloaking, I believe. Google's goal is to mimic a human user clicking through links and if the experience the bot gets is markedly different than others, that's a problem.
"Cloaking is essentially serving different content to users than Googlebot".
I'm a user who cannot view Quora content that Googlebot has indexed even though it was a result Google said matched my query. This result is therefore unusable without modifying the URL or signing in. That is the definition of different content, HTML/CSS/JS or other semantics be damned, and a poor user experience. And that's something Google is allegedly trying to avoid.
The Matt Cutts video also talks about mobile user experiences. If I worked for Quora, I'd pay close attention as I cannot view the site at all without getting their mobile app even though, again, Google said "you should check out this Quora link for this query".
•Using white text on a white background
•Locating text behind an image
•Using CSS to position text off-screen
•Setting the font size to 0
•Hiding a link by only linking one small character—for example,
a hyphen in the middle of a paragraph
`
When evaluating your site to see if it includes hidden text or links,
look for anything that's not easily viewable by visitors of your site.
Are any text or links there solely for search engines rather than
visitors?
From that enumeration none seems to apply. There is an image with blurred text, but no bad SEO practice to game a search engine bot.
You're right about the pages still appearing with high ranks on specific queries, but on the other hand I attribute it more to Google bombing than page relevance. At least I'm pretty sure Googlebot finds nothing to read on Quora, so the effect must be due to incoming links.
Since Googlebot will dutifully obey canonical, we now have link-bait to the original question with obscured content instead of the non-obscured answers. Again, this is gaming the system. You may disagree, and Quora may as well, regardless that's what's happening.
Edit: Link to webmaster guidelines on rel="canonical" :
Adding this link and attribute lets site owners identify sets of identical
content and suggest to Google: "Of all these pages with identical content,
this page is the most useful. Please prioritize it in search results."
Quora is gaming the system. Period. I won't pursue this point any further.
