Hello , you wrote at 01-26-2013 20:53

ask someone at google and quit reading / posting via google
groups. Use an appropriate newsreader and access via a newsserver -
there are a lot of them free available / accessable.

That less than helpful reply makes no sense to me. How does the way
I access rec.aviation.soaring have anything to do with the removal
of someone else's posting to the newsgroup?

newsgroups are mirrored to a lot of newsservers all around the world.
Using google as your accesss to the usenet is not the best choice for
several reasons.

In this case, for example, google groops doesn't show a posting any
more. But if you use another server like news.eternalseptember.org for
example (the server I use), the posting is still there :-)

Google !=internet, and usenet is far more than just google groups.

If google decides to remove a posting it is removed just from google
groups. Not from the usenet. There is no way to remove a posting from
all the usenet. The user who posted a message may send a cancel-message
afterwards and most (but by far not all) newsserver will delete the
posting ...

To at last answer your question "who has the power to flag it for
removal?" more exactly:

*No one has the power to remove any posting from usenet!*

But, of course, some google-employee (or script, or bot, or somewhat
else) may have the power to remove a posting from google groups.

regards
Werner