Found out about this game from a friend of mine on discord and I'm taking a look at the files. All the user input phrases are being kept in several .xlsx files under <GameRoot>/master and if I interpreted the JavaScript correctly, the game reads exclusively off this.
This is what the game likely does: A comment checker script checks the current scene being played by its ID (something like S14_QUIZ01), then takes the user's input and checks if it matches anything in the comment bank tagged with this scene ID, and if it finds a match, it will give the player an appropriate response (ie, the streamer reacting). If there is no match, it would likely just return with an "incorrect" response that encourages the player to keep guessing the correct input.
As far as I can tell, the user input is NOT case sensitive. The checking script utilizes RegExp with the i flag to make searching case-insensitive.
I haven't tested any of this, so forgive me if I get it wrong. I'd be happy to talk to you over discord if you'd like a little more help.