I think I understand the idea - but why not just let users with no Steem Power upvote without reward? So the "upvote" number goes up by one, but the reward does not change at all. Seems simpler.

I worry that reactions reduce actual interaction by reducing the friction too much. A user might leave a comment, but instead they just hit "worthwhile" and move on. It increases quantity but may reduce quality of interaction.

Being able to "flag" in a less aggressive way (to reduce payout w/o suggesting the content is terrible) DOES sound pretty good to me. That one part I do like.