Originally Posted by TheSquealer

How do we know when a discussion of bitcoins has gone from passive interest, discussion of new ideas, all possible outcomes to complete irrationality with an individual?

This answer is actually very simple.

Certainty.

Certainty, when it comes to beliefs and ones own internal representation of the world is simply the minds way of reinforcing the idea that your own representation of the world is perfectly correct. Certainty is how a brain defends itself from new information which might challenge it's own internal representation of the world.

What is a healthy position? What does a healthy mind do?

Doubt... You doubt what you believe. You question what you believe. You are open to new information and changing your beliefs and conclusions. What does doubt do? Doubt says you are willing to accept new information and are willing to change or expand your own internal representations of the world. Doubt makes room for new information. Certainty, rejects new information.

Have you ever seen a conspiracy theorist expressing doubt in their beliefs? Doubting their conclusions? Willing to accept new information which may challenge their views? Willing to say "oh, i guess 9/11 wasn't a government conspiracy"? Willing to accept they are wrong? Generally not. To what extent do they over generalize information? Shifting from specifics to broad and vague concepts "government", "authority" etc etc. Putting the presence or absence of mental disorders and disease aside, that's how you know there is something very off in how they are processing information and that they are clinging to a very distorted internal representation of the world and further distorting information to fit it into that model.

Conspiracy theorists typically are, above all things, 100% certain in their beliefs.

As user Camgirls said on GFY, (paraphrasing) "medications do not help stop the voices in my head, because the voices are real". He's made it clear that he's 100% certain of that fact.