My opinion:
Should comments be rewarded? Yes.
Should there be a separate comments pool? No. I don't see the point in that.

Here's a change I would propose.

Reward comments that are at least 100 characters long or 80 characters + pic/gif. Excessive ellipses would not count.

And if you don't want people upvoting their own content then simply remove the button. I personally do upvote my own content using SteemVoter after 30 minutes. Then again, I try not to post junk so technically I'm upvoting quality content. I can't be the only one who feels this way.