Yes, social scoring would be easy to implement. However for it to work you would need critical mass of people believing in it.
If you live in Minnesota and somebody in DC says that your score is low you can kinda just ignore it.
When you local milkman stops selling you milk because of it, then things get dark.
However your local milkman can already have "a score" for you which is even worse than that one from DC. E.g. not selling you milk because you are gay or have a green mohawk.
HN attracts specific technical audience who tends to see things from very technical (hard, logical) point of view. However what I want to stress here are "softer" things - how society works, how people interact, how they sell out, what they want to achieve with this etc. It is much harder to define and is much scarier TBH.
It might be a good idea to be nice to your neighbors, demonstrate only mild opinions, basically just "hide in a gray mass of people" before you start setting up your own email servers, degoogle yourself and etc if you are thinking about fascist government taking over.
For technology or corporations to betray you, you most probably be betrayed by society before that.
Did you ask the Chinese citizens in Chongqing if they can "just ignore" their social score coz they're not in Beijing?
The answer may surprise.
I understand that things would not so simple of course.
My main message is that technology is only a tool, it is still people, society doing the act.
It'll be easy as pie. The data is there in an easily consumable format. The tools exist to categorize and find undesirables. Tools exist which can be used to rank you in terms of desirability.
DC won't sent somebody to Minnesota because of what you wrote in a gmail alone. However, what you wrote in gmails would likely contribute to a "social scoring system" which would be used against you.