For some reason I couldn't get this test to pass on my machine with your code. In any case, using 'reload' seems kind of clunky. My test looked like this:

it "updates its cumulative score when a comment gets a score" do
  comment_1 = @link.comments.first
  comment_1.vote_up
       
  comment_2 = FactoryGirl.create(:comment, link:@link)
  2.times { comment_2.vote_up }
  
  @link.score.should == 5
end

And in link.rb my update_score method looked like this:

def update_score
  updated_score = self.comments.sum(:score)
  self.update_attribute(:score, updated_score)
end