Having finally obtained a copy of the Nobles expansion, I browsed through the rules threads here. There seems to be some confusion regarding the correct rules, which is understandable since the English translation is a bit dodgy. I got a copy of the original German rules from Stefan Brueck, who requested that I post here.
1. The German rules for the Villa state:
Kommt der Besitzer einer Villa in der Bürgermeisterphase das erste Mal an die Reihe, erhält er 1 zusätzlichen Adligen direkt aus dem Vorrat (also nicht vom Schiff!). Gibt es im Vorrat keinen Adligen mehr, erhält er stattdessen einen zusätzlichen Kolonisten.
Note that "zusätzlichen," which is emphasized in the original. It means "additional." So, the owner of a Villa gets a noble from the supply IN ADDITION to their normal pick from the ship.
2. The German rules for other tiles that refer to nobles all look like this example (Jeweler):
In jeder Aufseherphase erhält der Besitzer eines Juweliers pro eigenen Adligen 1 Dublone aus der Bank.
You will note there is no mention of "island" - it just says the owner of a Jeweler gets 1 doubloon per noble, period. None of the German rules refer to an "island," so all the arguments about whether that means just the plantations or not are moot - it was an unfortunate insertion by the English translator.