Something I've thought about (in the context of other venues) is a rating system where vote-totals V are stored but not displayed. Instead what gets displayed is a ranking R, where R=f(V)... a comment utility function, of sorts. That way a single vote in isolation does not cause a state transition.

The same function can apply to user "scores." Which may reduce the inclination to stress about one's karma, if one is inclined to that.

To pick a simple example, suppose (R=V^.37). So 1 upvote gets R1, but a second upvote stays R1. The 3rd upvote gets R2; the 12th gets R3; the 30th gets R4. Downvoting an R2 comment might bring it to R1, or it might not. Eliezer is R68, Yvain is R45, Alicorn is R37, cousinit and weidai and annasolomon are all R30, I'm R13, and so forth.

(The specific function is just intended for illustrative purposes.)

The function needn't be symmetrical around zero... e.g., if R=(-1*ABS(V)^.37) when V<0, rankings go negative faster than they go positive.

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Along a different axis, it might be interesting to allow voters to be nymous... for example, a preferences setting along those lines, or a mechanism for storing notes along with votes if one chooses to, visible on a different channel. The idea being that you can provide more detailed feedback without cluttering the comment-channel with meta-discussions about other comments.