Not all that surprisingly, there's quite a lot of discussion on LW about questions like

just what should get voted up or down?
what conclusions can one reasonably draw from getting downvoted?
should downvotes (or even upvotes) be accompanied by explanations?
should the way karma and voting work be changed?

This generally happens in dribs and drabs, typically in response to more specific questions of the form

Waaaa, how come my supremely insightful comment above is currently sitting at -69?

and therefore tends to clutter up discussions that are meant to be about something else. So maybe it's worth seeing if we can arrive at some sort of consensus about the general issues, at which point maybe we can write that up and refer newcomers to it.

(The outcome may be that we find that there's no consensus to be had. That would be useful information too.)

I'll kick things off with a few unfocused thoughts.

What voting is for: establishing the nearest thing we have to the consensus view of the LW community, so as to (1) help readers guess what might be most worth reading and (2) help writers adjust their writing (if they wish) to please the audience more. Note that these purposes are somewhat separate from ...

What karma is for: motivating people to participate, motivating people to participate well, giving readers an indication of which writers are most worth reading.

It seems to me that voting is working reasonably well -- I find a reasonable correlation between comment ratings and comment quality. I'm not convinced that karma is working so well; what's rewarded by the system is prolific posting at least as much as high-quality posting. Doing away with the auto-self-upvote (and making it impossible to upvote one's own comments) seems likely to be an improvement. Or maybe making each comment count for (say) 1/4 as much as an upvote.

Explanations for votes: Lots of comments get voted up; quite a lot get voted down. The practice of explaining votes (even just downvotes) would make for cluttered threads. Also: upvotes and downvotes are anonymous, which is largely a good thing. So, here's one possibility. (It might just be unnecessary complication). When you vote something up or down, you get the chance (or the obligation?) to write a brief explanation of why; it doesn't go into the thread as a comment, but gets associated with the comment you voted on (without your name attached). Then hovering over a comment's score (or something) could pop up a list of votes each way and their explanations, if any. Still anonymous; out of the way when not specifically asked for; but gives some hope of finding why something was downvoted, and also a way of distinguishing between +1 -0 and +14 -13.