what that appears to mean, literally, is "avoid use of the second-person, singular or plural. use, instead, elaborate constructs built around the odious 'one does this' etc..."
example:
"it would appear that it is not the content but, instead, the form of manners which matters here, one might be led -by some authoritative posts- to conclude."
Another good example of how not to be personal would be:
Right: "You did not understand me."
Wrong: "You do not understand."
The first case implies ineffective communication, while the second case implies the person who received the message is a complete moron.