I think it is kind of a gold mining of comments idea, if you spend all your time leaving well thought out comments on whale and dolphin posts then chances are you are going to see quite a few decent comment upvotes. If you are like me, and spend most of your time supporting and encouraging redfish and minnows then no you won't see much in rewards. I do now and again tidy up other peoples blog comments by upvoting the good ones to move them to the top, sometimes it can be luck more than judgement.
I think for redfish and minnows getting their posts seen and appreciated is still very difficult, where a good comment on the right post will get seen and rewarded well.