I believe that for a group to maintain good epistemic standards it's important for everyone to constantly lie to each other.
I heard a story once about a heavyweight wrestling champion who got into a car crash and then went to pick a fight with the other guy. He figured his years of practice and training would guarantee a win. Instead, the other guy did something which is illegal in wrestling - a punch to the head, I think - and knocked him out. The moral of the story is: things are different in the real world.
The path to good epistemics, I believe, requires a certain amount of explicit training, high-trust spaces where you can freely jump up meta levels and trust people to say literally exactly what they mean. But real life is not like that. So I say: practice your swings in the training room, and then when you've got the fundamentals down, start actually playing the game.
Unstructured play, with the truth, is the best way to get a feel for what kind of beast 'truth' actually is. I do think the game needs to be played in good spirits, and you need to be willing and able to stop when appropriate. But wow, people will fall for a lot! I am constantly surprised by how readily people will accept extremely unlikely claims, big and small.
Myself, I am not much better, but insofar as I am any better it's because for most of my life, people I liked and respected would lie to me all the time. And often they were kind enough to point out when I'd fallen for it. I recommend it!