When I want to delete a posting, I select it and press the delete key.
BUT, but the big difference is I'm using a real newsgroup reader
(Mozilla Thunderbird) and your using some web site as a front it to the
newsgroup network.
And even though I *can* delete a posting, the fact is that once sent a
posting will radiate through the entire network of newsgroup servers
that exist throughout the world. That posting probably will go to
untold thousands (millions?) of servers/machines around the world and
will not respond to my meager request to "please delete me" even though
on my PC I have the peace of mind to see that the posting has vanished.
But it does not vanish and lives on in many places.
Your use of the newsgroup network is via that web server you use. I
don't know what that it is. Anybody can provide a front end to the
newsgroup network. You are using one of those front ends and it
apparently has bugs (won't notify you even though it says it will).
Contact the people who run this web site and ask them to fix the bug.
See
http://en.wikipedia.org/wiki/Usenet for the original of the
newsgroup network (called Usenet).
--rms
www.rmschneider.com