@Ringing_Nirnroot I think there is a workaround for this, in that you can change your keybindings - I think you can set it so that your Vampire feed and Assassinate keys are different.

I originally changed it on one of my characters, mostly to avoid accidentally hitting X when my dungeon finder prompt finally popped - D'Oh! The default interaction prompt also affects things like accepting/deleting emails though, so it takes a lot of adjusting time. Eventually I was just not happy with being a vamp tho, so "cured" it..

Mostly you just have to be super-careful about the distance at which you try to backstab someone with the BoW. It works fine up close on my remaining vamp - the "feed" prompt only appears if further away.