Please correct me if I am wrong, but, if you do not leave the auto gratuities on your bill then anything collected by individuals has to be put 'in the pot'. If you leave the grats on then anything extra you give can be kept by the individual. The same staff work the buffet area as in the dining room. They all take shifts and bus tables, get drinks, etc. The gratuities are divided between staff - behind the scene too - so whether you leave it on your final bill or do it individually it will be split. It is my understanding that you must go to the front desk to remove the auto gratuities and they will ask you why and what was not up to standard.