Or you could suggest graphics or + or – signs as the first item in the comment; then you could just scan through the comments and collect all the ones that are each. Ignore the ones that don’t follow the instruction.
I have thought of doing something similar in regard to a certain highway interchange (the ultimate photo challenge:P), but am not sure I would want to go through that much trouble. I am not sure even if potential voters would want to go through that much trouble. It sure is nice on message boards to click a vote and see all the results pretty much instantly.