The Extension actually does nothing, but invert (make them upside down) a few words on specific sites.
It's an experiment called "PUG ARG" to check whether page contents sniffing works. Its page doesn't reference any Bugzilla issue or Wiki page, while https://wiki.mozilla.org/Firefox/Shield/Shield_Studies/Queue doesn't list it.
The source code references https://support.mozilla.org/kb/lookingglass, which (as of now) only says "test - 12817".
The add-on tests whether specific words can be detected on sites; the current list has nice picks like "revolution" and "privacy". Of course, this is only a test, but in the future Firefox might look for specific terms in the pages you load and do specific things based on them.
The other thing it's doing is to send an extra header to three specific sites: https://github.com/gregglind/addon-wr/blob/da464ac8f1c3b0894.... I suppose the words and the domain are a reference to the Mr. Robot series.
The add-on describes itself as an "Augmented Reality Game Experience" and was made by a certain "PUG Experience Group": https://github.com/gregglind/addon-wr/blob/da464ac8f1c3b0894....
Of course, Shield Studies are supposed to be a way of making "more informed product decisions based on actual user needs".
https://www.reddit.com/r/firefox/comments/7jh9rv/what_is_loo...