Er...I would really keep my hand away from the food, as mentioned before. Either the mantis will associate it with food, or may possibly feel threatened that you have taken 'their' food, which used to come on a non-threatening stick,etc... And these animals are capable of immense force, especially the Peacocks (My 2 G chiraga are no slouches either).
Different note, but relavent to hands in the tank, and pretty funny...
As far as infection from the tanks, bacteria,etc... I had some sort of polyps a couple of years ago,when I first started keeping tanks. They just appeared one day on some LR (They have since died/disappeared...). Anyways, I work in a nightclub, and I frequently cut myself at work, behind the bar is a dangerous place with glass bottles and dim lighting. I was target feeding the polyps, as they loved grabbing onto pieces of krill etc... and I accidently stabbed one with the feeding stick. The polys either 'bled' or shot out some sort of liquid, be it a defence agent against attack or it's vital fluids.
I thought nothing of it, and my cuts on my hands...
About an hour later, as I was setting up my bars, I started to have a feeling similar to one that I 'might' have had if I had ever done hallucinogens (Which are illlegal, so of course I have never done them...). I got dizzy, my vision blurred and my thoghts became really scrambled. I sat down and was still reeling, on a bad 'trip' 30 minutes later when the GM came in. He spotted me, came over and asked if I was OK. I couldn't even formulate a proper sentence, and my joints were stiffening up and I was sweating profusely as well. He then asked if I was 'on something', knowing that I would never do that before work (Or ever, since it is illegal...), and that there must be something wrong with me.
I tried for 5 minutes to explain that I had been working in my tank, and an evil LSD polyp has 'dosed' me...I ended up having to have someone else work my shift, and should have gone to the hospital (I intended to, but my brain was scrambled, remember...), but instead I went home and had a bad night of attempted sleep.
That indiscretion (No gloves, which I had just bought...stupid me) cost me about 400 bucks in tips (Er, I mean...50 bucks, Mr. IRS man...), and taught me a lesson about exposed skin in my aquariums.
OK, long-winded, but I hope that it helps make the point in favor of safety.
And yes, my mantis are all very cute, as are my begging lion fish, and I want to be their friend, and hand feed them, but I like my health too much to give in to that.
-Uriel