I've dabbled in commentrewarder a bit, and it seems to work well. Spammers don't get any automatic rewards, and I (you) choose which comments get a piece of the pie by upvoting then to any degree.
The Art of Manliness just released a podcast about how to write engaging content. Check it out here if it interests you.
Yes, commentrewarder does seem to do the job. To wit, see screen shot below of this post and my post from the day before... both of which have similar rewards and number of upvotes.
I'll check out the podcast; thanks for the recommendation!