They can be. But if they are shallow, dogmatic assertions, they often (and should) go negative and stay negative.

I've seen lots of good, fair comments with strong opinions (whether I agree with them or not) go initially negative -- early downvotes from the anonymous censorious underemployed peanut gallery -- then creep back up to small positive values after a full day's cycle. Those are much better comments than any pandering +20 one-liner.