User blog comment:ZoloLover/luffy's message to his crew?/@comment-110.233.173.16-20100801144617

I don't think Luffy would get a TATOO just to tell his crew a one-time message. And have you noticed that a few pages later the "tatoo" is gone? (The scene where the Kuja girls were pinching him.) I think the message has something to do with both the 16 rings and the mark on his arm.