This post is somewhat confused. I would recommend that you finish reading the Sequences before making a future post.

any object in a thought experiment cannot be tested for but still has a meaning.

One way to think about what is accomplished when you perform a thought experiment is that you are performing an experiment where the subject is your brain. The goal is to figure out what your brain thinks will happen, and statements about such things are falsifiable statements about brains.

Anthony gave the argument that if believing in a dragon in your garage gave you happiness and the world would be the same either way besides the happiness combined with the principle that rationality is the art of systematized winning it is clearly rational to believe in the dragon.

The world is not the same either way because the dragon-believer is not the same either way. If the dragon-believer actually believes that there's a dragon in her garage (as opposed to believing in her belief that she has a dragon in her garage), that belief can affect how she makes other decisions. Truths are entangled and lies are contagious.

I responded with truth trumps happiness

Why?

The belief has a beauty to it that flows with falsifiable beliefs and makes known facts fit more perfectly. (this is very dangerous and should not be used lightly because it focuses to closely on opinion)

Can you give some examples of beliefs with this property?

You believe that the belief will someday allow you to make an original theory which will be falsifiable.

Why call it a belief instead of an idea, then? (And why the emphasis on originality?)