Well the quote you mentioned, "Brother of the Society of the Black Cloak" doesn't even look like something I wrote in the page. its from one of the other people that wrote that article before I added to it(you can check the history for yourself, see the article update by connor in august 2005, before I even came along). It can easily be removed from the article for more accuracy sake.
Actually it looks more like it should refer to the quote, "Alhazred brother of the Black Cloak". I've changed the order of the sentence to relfect that quote.
As a side note reading back through the King's Quest companion it brings up a rather interesting factoid about Alhazred while he is a friend of Mordack's, he is actually a subserviant minion of Mordack's. Which places Mordack at a higher position over Alhazred.
Mordack is connected to Black Cloak society but how much is unclear, if he is outside individual who is friends with members or as a member himself, who knows. But the important matter was that he actually held command of the Viziers actions and was apparently in on, and or concocted the plan for the takeover and destruction of the Green Isles. Including Casimma's kidnapping.
Other than that, the thing you need to remember about the omnipedia is its a form of the wikipedia. In that anyone can add or change anything on the site. That is articles are written by multiple people. If you notice something that seems flawed to you, you can easily alter it yourself.
I mostly add to site and avoid altering other people's additions. Unless I specifically noticed a disecrpency. But I'm human, and sometimes things do get past me. ....or I didn't read the entire article, instead just skimming through it, and just expanded where the article left off.