When you grant moderation points on slashdot, you can moderate them not +1 or -1, you have a set of choices like:
+1: Interesting, Informative, Funny, Inspired.
-1: Redundant, flamebait, troll, provocation
The result is something like this: http://linux.slashdot.org/article.pl?sid=08/10/10/1520200
Here on brainstorm we can implement something similar to ask the voters the reason why they voted that way. My suggestion is to set something like:
+1: Interesting, Handful, Useful, Necessary, I like it.
-1: Not and Idea, Unnecesary, Useless, Incomplete, I don't like it.
Of course, can be modifieds.
This ideais for avoid "blind" votes.