That isn't a rule of thumb at all, just your opinion...
I don't think it makes sense to make things denser if it's going to be so ugly that no one wants to live there.
Very rarely, if ever, are buildings "so ugly that no one wants to live there", especially when places to live are as scarce as they are in SFBA.
also, transit oriented development: https://en.wikipedia.org/wiki/Transit-oriented_development
That isn't a rule of thumb at all, just your opinion...
I don't think it makes sense to make things denser if it's going to be so ugly that no one wants to live there.
Very rarely, if ever, are buildings "so ugly that no one wants to live there", especially when places to live are as scarce as they are in SFBA.
also, transit oriented development: https://en.wikipedia.org/wiki/Transit-oriented_development