You're writing as if family names were / have never been a thing. Characters across an account can be forced to share the same last name, and all reps can be applied account-wide so that people can't just have one character that remains friendly to all factions. There are methods being used in other games to allow multiple characters while maintaining the community interaction you profess to be protecting.
That statement implies that I am the one championing the one character per account policy. I don't know where you got that idea, as I clearly said if multiple characters were allowed per account, I would play multiple characters.
What I said was that "everyone will be reliant on intra and inter dependent relationships with those around them which, like the real world, is how communities are built". That is a simple statement of fact. The less often players have to go to others for goods or services, the less activity exists between players, leading to a lower sense of community. It's also a fact that because this is a game with less consequences for behaving badly with others (as compared to the real world), that the successful building of a community using this enforced interactions mechanic is not assured.