I think it's a wild and varied and disorganized mess dreamed up by people who have left the very idea of being reasonable far behind them long ago.

However, a crucial part of it is certain specific capitalization of words. I think some of them had been using caps lock to post rants on discus for too long and think that it has some magical meaning under law...

I say all that to say that they believe that there's a "legal entity" that is invoked when you capitalize versus plain case someone's name (amongst other things)...and that there is a difference between this "legal entity" and the person in a body...which there frankly plainly and obviously isn't.

Despite being told in court by multiple judges that the capitalization of things does not matter, they persist.

https://en.wikipedia.org/wiki/Sovereign_citizen_movement#Immunity_from_laws_and_taxes

I thought the capitalization stuff was kind of a side show, but have since realized that not only is it crucial to their belief system, it also serves as a way to identify them on the Internet. If someone strangely insists on capitalizing certain words or phrases every time they use them and is otherwise very unreasonable, there's a good chance they're a sovcit (or should I say SOVCIT? 🙂).