I agree the front office does indeed release the cabin no. of those who remove the tip. As for removing the tip, they will have to turn in the required amount,, any extra ( above their portion, say 3:50 pp for the waiter) they can keep.
I agree with OM, just leave the auto tip on and personally hand out any extras in cash yourself. If service is poor, then wait till last day and have them( tips) adjusted, be sure to mention who you are specifically unhappy with( restaurant stafff or cabin staff) .
Never had bad service myself, course I give everyone the benefit of the doubt and do realize staff are humans and have bad days just like we do. I would never remove a tip for one instance of poor serivice.