Humm, I have never heard of hand feeding as a way to teach respect.
I never hand feed. What it does encourage is nibbling which can lead to bitting. Also creates a horse that is constantly pushing you for attention and treats.
I give treats, I just put them in a pan, then give them to Christy. She does not bite, nibble, or push. My friends horses (all 3) do bite, nibble and push, she hand feeds them treats.
So, I guess for me, not hand feeding creates more respect for me, and my space. Christy looks for her treats, she just doesn't try to get them from my hands or pockets, she goes to her little treat pan. Or, on occasion, brings me her treat pan...