I asked this before, but as I got no answer, I am posting it, again.
I have added some words to the stop words list in "NutchAnalysis.java" (for instance, "da" and "de" - the same as "of" in english). After that I indexed some sites and, then, some searching. I got "zero" results for the original words, already in the list, but a lot of undesirable results for any of the added words.
It shall be noted that I added that same words to the "common-terms.utf8".
As this is a issue that I have noted, since the earliers releases of Nutch, I would be happy if someone could explain this behaviour.