What A/B testing platform does Quora use?

Someone from Quora can confirm this, but based on what I have observed, I don't think they are using any third party tool for A/B testing.

I use a tool called Ghostery (browser extension) for this purpose. If the website is using any of the popular third party platforms for web-analytics, tag-management, ad-serving, or A/B testing, Ghostery will be able to detect those. Of course, if you are doing this in-house, it won't detect anything.

This is what Ghostery detected for Quora:

So, it does not appear that they are using any of the popular third party tools.

Ghostery does detect most third party A/B testing tools, if present:
Optimizely – Analysis by Ghostery
Adobe Digital Marketing (Omniture)
Visual Website Optimiser (Wingify)

See question on Quora