In this case, the content was already in a post.

Mechanically, I'm not sure how you'd handle automatically upvoting articles into Discussion: people do that by hand often, but they have to do it by hand because most contents lose usefulness and sometimes even readability when pulled from context.

((At a deeper level, it's quite easy to imagine or select posts that belong in Discussion or solely as comment and will quickly get high Karma values, and just as easy to think of posts that belong in Main but shouldn't have anything that would make folk upvote them to start with.))

The main problem with karma sorting is that the people that actually control things are the ones that read through all content, indiscriminately.

At least at this point, it's easy enough (and often necessary enough) to change Sorting regularly just to find an article more than once, so I'm not sure sorting is the most meaningful part of Karma. The ability to prevent posters from regularly creating Main articles seems more relevant, and a number of folk at least treat Main articles more seriously.