Graham
I figured out why the 'related posts' disappears after posting a comment
The
__xtblog_entry value is missing from the comment form
(The html is there but the
data.comments_form.entry_id value is missing from the blog data array)
to correct this replace
<input type="hidden" name="__xtblog_entry" value="{{ data.comments_form.entry_id }}" />
with
In the main comment form