Actually it was not a reply. I suspect S (come on, a bit more
originality, please) meant to reply to someone's post but instead
created a new post. There is no References header in his post which
would be present if S actually had *replied* to someone else's post.
Probably clicked the New button instead of Reply Group button, also
inferred because S had nothing of the original post in S's message. The
joys of using a web interface to newsgroups.