Mmh, while I do understand your viewpoint I don’t like the idea. But I don’t like the current situation neither. It took some time before I noticed that upvoted comment climb the ranks in posting.
Your idea, which is much better than no idea, would give me the feeling that my comment would be worth less based on my time in the steem-eco-system. It could created the idea that whales are dolphins are more valuable.
It is at the moment hard enough for newcomers to get noticed and this would make it even harder.
For me personally I would just like them in posting order. Which would make it easier to see if I did read them all or which are the unread ones.
So I don’t want to critize your idea, just want to give you an other perspective!