My view of Karma is similar to my view of money: it's an artificial measure of the value you add to this site.
Most of my Karma comes from comments because I honestly take a pretty passive role here, taking in and commenting instead of actively adding nodes; however, I have an interesting habit. Whenever I write a comment, before I submit, I double check to see what value I'm really adding. If it's not pretty significant — if my comment is pretty much just agreement with something someone said with little additional information — I drop it and just upmod. It's a small effort to try to bring up the signal-to-noise ratio recognizing that even well meaning comments can be be noisy.
The part I want to call attention to is that, to me, it seems like you're still adding value when you upmod. It's far less than a full comment or submission, but you're calling attention to signal instead of noise.
My suggestion is that Karma could be incremented based on some fraction of the number of upmods that occur on an article you upmodded after you did so. This rewards the people who read articles (especially those on the new page) and vote so as to bring attention to something interesting.
Sound interesting?