Hi, I'm one of the devs on the Ai2 Playground! That's an unfortunate consequence of a compromise we had to make for technical reasons. You need to click the "Show OlmoTrace" button below a response to see span highlights. The first time you click it will take a few seconds, but it'll show highlights after it loads! The paper button at the top opens the popup that contains documents for the message you selected by clicking the "Show OlmoTrace" button.

Appreciate you posting about the issues you're having with it! It was difficult to figure out how to show this well and we'll be taking your experience into account.