This article has a Reply-To header field (which you can see via the "Original Format" link). However in the HTML presentation of the article, not only is this field not visible but also the From: field is presented as the proper reply address.
The relevant text of RFC1036 is section 2.2.1:
2.2.1. Reply-To
This line has the same format as "From". If present, mailed replies
to the author should be sent to the name given here. Otherwise,
replies are mailed to the name on the "From" line. (This does not
prevent additional copies from being sent to recipients named by the
replier, or on "To" or "Cc" lines.) The full name may be optionally
given, in parentheses, as in the "From" line.
Google plainly fails to cause mailed replies to go to the right place, and in fact makes it hard to work around this deficiency. In the case of the example article this is potentially quite a serious problem; its author is apparently treating the sending of replies sent to the From: field rather than the Reply-To: field as a spam signature.
I mailed Google about this on 2002-04-30, but have yet to receive anything other than an autoresponse in reply, and put up this page out of pique at being apparently ignored. If anyone notices that they've fixed this, please let me know.