They're not currently counted any differently, we discussed it when the wiki karma plugin was initially put together. I'm not sure if MediaWiki actually differentiates between regular and minor edits when counting total user edits. . . .

Basically, the wiki system makes it rather difficult to quantify the value of any individual edit. Technical issues aside, character count doesn't really tell you anything meaningful and you can't usually rely on editors to consistently check the appropriate boxes when submitting a change. This is no different than Talk, the lists or Bugzilla. The karma multiplier just needs to be kept sane to account for this.