From the whitepaper:

One of the primary goals of Steem's reward system is to produce the best discussions on the internet

That's why I find that interesting.
I don't see good comments being rewarded

Good discussion requires back and forth posting. When you reply to someone else they get 50% of any payout you receive in that thread [...]

This hasn't been implemented yet, or I don't understand it right ...

Until then it would be nice to see, why and how comments get a reward.
Especially from whales.