Michael Press writes:

He chose it because it put special emphasis on the phrase as the OP
probably did. By the way, changing the title loses the thread and
starts a new one, which is also none too good for tracking where
the discussion arose.

No, changing the subject header does not change alter the threading.
The References header and In-Reply-To header maintain integrity. A
correctly written news reader is capable of displaying the list of
articles according to the References headers. Still the user must
choose to display the available articles according to threading if
that is what he wants, and not depend upon the article Subject
headers to organize the threading. Changing the Subject header in a
sub-thread is permissible, even preferable, in many cases.

Speak for your own news reader. Tin, the UNIX threaded news reader
that I use, keeps threads by title and lists them only once even if
cross posted to several subscribed newsgroups. Unless the item is
separately posted to each newsgroup, it will be flagged as "read" once
it has been accessed by the user.

In this case I came across the item under separate threads.

Jobst Brandt