In the post-based inbox, comments are sorted by related posts. The Post-based Inbox is displayed as an additional folder in the Inbox below the Inbox.
Within the post inbox, you will then see the respective post and in the top right-hand corner you will find a speech bubble with a number next to it. The number shows you how many comments there were on this post and if you click on the balloon, the corresponding comments are displayed and you can edit them.