Google's John Mueller said on Reddit "A site is not going to outrank your site just because of hidden text." He also added "Inversely, just having hidden text on a page won't get the site banned from Google."
Google uses many signals for ranking, John explained. He said "Lots of sites get things wrong, lots of sites have text accidentally hidden (or even purposely hidden until you interact with the UI) -- sites aren't perfect and so our algorithms work to deal with these imperfections in a reasonable way. Sometimes that means the top ranking site - the one our algorithms currently think is a good match for a user's query - is one that does a lot of things technically incorrect."
The person who started this Reddit thread wrote "My Competition is cheating – is there anything i can do?" He explained "Two of my biggest competitors use invisible keyword stuffing text." Well, it isn't that simple John Mueller from Google is saying.
Also he posted this today on Twitter:
Let me tell you a secret: there are lots & lots of algorithms, and you don't have to win at every one of them to be successful in search.
— 🍌 John 🍌 (@JohnMu) January 22, 2020
Forum discussion at Reddit.