Hi Esi -
Look for the task in your account. It should still be in the queue where you created it. You can also search for it.
On the task, you should see the comment next to the person you assigned the task to.
Right now, only people assigned tasks can add a comment to the assignment. It's not possible for task owner's to reply to the comment (unless they send an email).
We are building out a full-fledged, threaded comments feature. It's currently in beta and will launch in the coming months.
-Cameron