Hm, I'm not sure I agree with that one entirely. It seems to be the popular opinion that a writer is not allowed to get really emotionally invested in their characters unless it's going to culminate in bad writing, but I don't buy into it.
How can you possibly write about something you're not invested in, neck and crop?
I act out whole dialogues in front of a mirror, I have a ritual of getting myself to sleep which involves imagining I'm one of my characters and developing some scene. In fact, I go through most of my daily routine with some character sitting in the back of my head.
My beta tells me that the characters for which I do this have the most dimension, while those for whom I don't tend to fall flat.
Diversity is not a matter of holding your characters at an arms length at all cost. It's a matter of flexibility within your own mind.
Sure, eventually, I have to distance myself from the characters in order to avoid Narm
and Creator's Pet
and whatever in the writing process.
But that's how I create characters and I refuse to believe that it's necessarily a mark of bad writing.
Complicated - because simple is simply too simple.