Proper Punishment for Parrot Perdition, in Pirate's Cove
There is, unfortunately, no official ruling.  You can attempt to get one by contacting Days of Wonder directly: Question Submission Form.  However, as it's a popular question and no answer has appeared for some time, I wouldn't hold my breath.  

As with any rules dispute, I highly suggest the group agree on a strategy for resolution beforehand (for all games).  My group usually does not like to halt the action, so we take a quick vote, go with the majority (or flip a coin on a tie), and then look it up later.

As for my personal opinion, Pirates Cove makes no distinction between Fame and Notoriety, so when even bad press is good press, the concept of being 'less than a nobody' doesn't make much sense.  All the pirates start out as absolute nobodies, and there's no where else to go but up.

A better defense than theme is that many games which take into account the possibility of going negative will often give an in-game way of tracking that, such as a -1 token, card (e.g. dominion's curse cards), or to start the players out with some points to lose.  Since this game did none of those and there are not explicit negative numbers on the fame track, the evidence points towards no negative fame.