(Thanks to jmalcolm@sura.net (Joseph Malcolm) for supplying
these answers.)

>1) Why did my local INN act on the sendsys posted to to.neighbor?

to.* groups aren't magic to INN.  Your system received the message,
it acted on it.

>2) Why did my neighbor send the cmsg to all of his neighbors?

See 3.

>3) Is is related to having the "control" group in our newsgroups patterns?

Yes.

>   The INN docs say you probably don't want to do this, but they don't say
>   why.

Actually, they do. This is from innd(8):

	Sites may explicitly have the ``control'' newsgroup in their
	subscription  list,  although  it is usually best to exclude
	it.  If a control message is posted to a  group  whose  name
	ends  with  the  four characters ``.ctl'' then the suffix is
	stripped off and what is left is used  as  the  group  name.
	For  example,  a cancel message posted to ``news.admin.misc.ctl''
	will be sent to all sites that subscribe to  ``control''  or
	``news.admin.misc''.

There is also a pointer to this in newsfeeds(5).

>   But I still need it in my active file, right?

Yes.

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