It seems that if you look at the column on the right of the page, you can see upvotes and downvotes separately for recent posts. The same [n, m] format is displayed for recent comments, but it doesn't seem to actually sync with the score displaying on the comment. This feature only seems available on the sidebar: looking at the actual comment or post doesn't give you this information.
Thanks, whoever did this!
It's very useful feedback. I have 82% positive. Going through my old comments, I found that a lot of comments I've made that I thought would be controversial actually had 100%. The comments that had a low percentage tended to be the ones where I hadn't expressed myself well. Given that I have a lot of unorthodox views, I found this reassuring.