I like to believe most of them are trolls, but you can never be too sure. Some of those comments actually do ask decent questions regarding refraction and line-of-sight calculations.
I believe that a significant number are true believers, judging from conversations I've had with them in the past.
The conversations I've had with them have lead me to the opposite conclusion -- they are so good at their presentation, I figure they may be working on their acting or debate skills. A true test of how good someone is at debate, is if they can win arguing for the opposite of what they believe.
I believe that's essentially how the Flat Earth Society started, and then spiralled out of control as people actually started believing it.
Is there a way to make a correct distinction?
Not in an anonymous forum where they can't even lose reputation.