That's not a bug, that's on purpose, according to @jmatazzoni 's spec for the first-run of the usable mobile page.

The issue was that when dates appeared, the entire line was extremely long and started pushing the "mark section as read" down a line, which looked very awkward. @jmatazzoni requested we hide the "subtitle" (full date) for the moment.

We can reconsider the entire design when we work on the second iteration of the page.