A lot of people get confused by Drain. Here is how it works (in basejka, as opposed to some wacky mod):
SP: Steals enemy's health and gives it to you. (and you can grab them at close range!)
MP: Steals enemy's Force mana and gives you health in exchange. (you can't grab them, period)
Also, IIRC in MP, we discovered through testing that if you drain somebody that has Absorb on, you don't steal mana, and I'm fairly sure the person using Absorb does get mana back (assuming they have a high enough level to completely counter the power).
I didn't really want to jump heavily into this debate since I'm not really much of a duelist, but when people say "bunny hopping" they mean rapid use of normal jump (not force jump) with strafing and running. So technically the act of "bunny hopping" itself doesn't use any mana.