What qualifies as a complaint is so subjective. Is telling my finace all about my day (even the bad parts) complaining? If a certain co-worker screws up yet another customer's order, is making sure management knows about this problem complaining?
I don't see Jilly simply stating her belief that this challenge would be difficult as complaining, for example, but she does. Does that make sense?
I couldn't pledge to take on this challenge, simply because the line is so blurry. Best of luck to those brave enough to try it, though!