Perhaps the karma system of LW should include a reason why someone voted text up or down. Reasons for upvote could be like "interesting", "well referenced" etc., reasons for downvote could be like "useless", "offensive" or "insane".

Suggested implementation: Clicking upvote or downvote could make a tiny textbox next to the thumb appear where you can (but are NOT obliged to) type a maximum of 15 letters, explaining the vote in one word.

Reasons for upvotes appear in tiny green letters, reasons for downvotes appear in tiny red letters. Identical words are not repeated but a +<number of times mentioned> can appear next to them.