I think devoting a large slice of the reward pool to comments is a great idea (for context, see: proposal). A lot more people are comfortable writing comments than authoring posts. But the incentive just isn't there at the moment.
Once this dedicated comment reward pool is funded, there's a real incentive to engage with the platform. Yes, there's a possibility of $1,000 comments. One time, I wrote a comment that earned $781.50, and that was under the current reward pool.
But that's great. The possibility of huge payout is one of the things that makes steemit compelling to content creators. Why not open that possibility up to comments?
Does that mean we'll have more comment spam? Yes. I'm for it. Because that will reduce the amount of post spam.