Q:

Suggestion to reinstate the divider between the post and the first comment

Since the new design update I found myself reading the first comment as being part of the question a few times.  A divider would be a better indication that you're at the comment section. 
Current situation

Proposed situation

It's also more consistent with the look and feel of the other comments, the current situation makes the first comment stand out. 

A:

I have added a divider line per your suggestion.  It will be on live after the next production build.