The first time I saw the feature that lets you click on the votes for a question/answer to see the number of plus and minus votes, I thought it was a bug. I noticed it because I missed the arrow button I was aiming for. I remember trying to click on it again to see if that would do anything, but it didn't. So, I chalked it up to some strange javascript bug. I eventually learned what the feature was, but my first experience with it was that something was wrong.
I think this could be easily remedied by simply allowing users to toggle between net votes and plus/minus votes rather than only allowing them the one-time switch. A user would click once, think, "Hmm, that's strange." then click again and see it "go back to normal". After toggling a couple times, the feature's meaning would (hopefully) become apparent. It would also be nice to be able to return things to "normal" even if you know what the feature does, but I think the main benefit is making it more obvious that this is an intentional feature, not a bug.