BM and his note.
 

Way back, around comic 500, BM wrote a rather touching note to WM. That note was apparently heart felt, and it was surprisingly non-evil. What was with that? Does BM have a side, besides his evil and atrociously evil side, that is being suppressed somehow? Was there ever any indication besides this that BM might have some sort of buried good side

There was one comic even before that where he had a long internal monologue about whether he controlled Black Magic or whether Black Magic controlled him, concluded he would be better off making an effort to use his power for good rather than act on evil impulses. Then he got distracted by an especially stupid remark from Fighter, couldn't remember his train of thought and murdered everyone, figuring "well, whatever it was, I'm sure this isn't too far off the mark."

(It happened while they were on their way out of Marsh Cave, if anyone wants to go look for it; somewhere around the 350-400 mark if I had to guess, but this could be completely wrong.)

It's wholly possible that the reason BM has gotten "dumber" as the comic progresses is more than simple comedy. It could be a case where the more he abuses his powers, the more they control him, and his stupidity is merely him being kept in the dark by outside forces, as it were. However, this is purely theoretical, and most likely about as far off the mark as one could possibly be without falling of the goddamn map.

Nope.
It's just that Brian can't write serious drama that well.
(If my plan works we might see serious drama along the comedy, yaaay)

The comics Awake and Meister are talking about, if anyone's curious:
-289
-486

My theory is, that BM does have a nice side, but his Evil Side and his Atrociously Evil side teamed up and locked in in a cage in his mind, somwhere between the "stab Fighter" and the "Beginn Armagedon" sections.

Whenever Evil and Atrociously Evil take a nap, Nice comes out for barely 20 seconds, before Evil and AEvil cage him again.

I have a theory on this:

Originally, for the first few comics, Black Mage played the role of Evil Genius surrounded by morons.

Later, thief took this role.

Since thief was supposed to be an evil genius surrounded by morons, it made no sense for black mage to not be an idiot. It would mean that thief was surrounded by morons and one evil genius. So, black mage became stupid. Since its funnier that way.

Also, if you care about continuity at all, we'll just say that he spent too much time in a room with fighter. Believe it or not, stupid IS contagious.

I don't think White Mage became a minor character right after the note, maybe just an occasional character. She still created the universe, rebuilt Onrac, and had that whole evil thing. If anything, she became a minor character after they reached Dragoon's tower, as she's only had like 7 or 8 appearances since then.

Maybe, just maybe, Brian's basing the personalities of his characters on real psychological disorders, and BM actually has a form of Tourette's that causes him to say the most horrible things that spring to mind. After a while, he's gotten used to having to follow through with those statements because people beat him up for mouthing off otherwise. >_>