Was pondering more about Manousos' fear of theft (he hides money in his ceiling lamp, he says everyone's souls have been stolen, he tells the Others everything they have is stolen) as well as his fear of being a thief. He refuses to take anything without paying for it, and some of that is likely, as others have pointed out, rigid autistic Sense of Justice, but I think there's a piece missing. So for fanfic purposes, I started researching. What exactly happened in Colombia that could make this man terrified of theft?
I found out about expropriation.
Note that this paragraph is talking about a specific incident that took place in 2001 and involves a rural village, but that this was also happening for decades around Bogotá. So you could well be a city dweller and still have the state evict you to acquiese to American/European corporations.
There was a large wave of evictions in Bogotá in the 1980s and 1990s, which would line up with Manousos' childhood or early adult years.
If you were forced to leave your home, if your land was taken from you, if your family had to move because of this, it would indeed be a form of theft, and cause generational trauma. (And I wonder if it also had anything to do with the death of his father). The horror of the idea of ever being like the people who hurt you (thieves) could indeed install a deep moral conviction in a young person. They hurt you so badly, that you never want to be like them. So you pay for everything in an almost pathological manner to soothe yourself. This trauma response would be ten times worse if you were an undiagnosed autistic kid.
It's important to remember that while the American/European corporations that did this are scum, the state is also at fault here. And Carlos-Manuel Vesga has gone on record as saying: "Manousos hates corrupt politicians and liars."
I come from a Latin American country (I don't live there now, but my family does) and while rich Americans do tend to move in and do whatever they like, they wouldn't be able to if our government didn't let them. Often when LATAM people bring up their own country's corruption I see a lot of Americans on here be really shitty to them. For example, lots of people from the USA called Venezuelans "gusanos" because they had the gall to say that even though they hated Trump, Maduro was still a corrupt dictator. I cannot imagine the level of arrogance some Americans confidently hold to tell Venezuelans they know better than them about their own country's politics lol.
If Manousos' backstory does involve expropriation, I'm hoping the show has this more nuanced take and calls out both the USA and the local state for their combined corruption. I can see a lesser show just writing this out entirely.
I have a feeling it will be handled well, as this group of writers tend to be very careful and nuanced with character development.
Of course, this is all speculation, and maybe this has nothing to do with his backstory at all.