So I'm really enjoying this commenting feature. It's nice to be able to react to reviews beyond that which is possible with the helpful / not helpful buttons.
But the obvious weakness of the feature is that there's no way to tell which reviews have comments. There's also no way to react to a review directly from the recent reviews page.
We're working on it.
Here are the two improvements that will be going live shortly:
1) We will display how many comments a given review has on the individual listing page (the page that aggregates the various reviews.)
2) We will provide a link to comment on reviews from the recent reviews page.
Feel free to send in other suggestions as to how we can get the most out of this new feature.