There are several comments that are printed in a black bar on the actual bag tags. Off the top of my head that I have seen are PRIORITY, NON-REV, LATE, HEAVY, and DAMAGED. It is not very noticeable (it is only on one side) and other than putting a matching code on your claim reciept, doesn't do too much as far as I can tell.

The theory behind the purple band that says PRIORITY is that these bags will be loaded last, offloaded first and down to claim towards the begining, although, even on a flight with 40+ Assent/Summit members I can't remember that happening.