Bad service...reduce the tip accordingly and drop a note to the department head. Good service...increase the tip.
Wanna bet bet that slimoid brags to her friends how she stiffs the service staff on her cruises? Wanna bet she always changes ships? Wanna bet she is the one we have all seen whining about service levels, etc?
There are times when you wish you could revoke membership in the human race from some of our more "fringe" members?