Meaning and purpose of the Subject field (was: Ignore error with non-zero exit status)

[Cameron Simpson]

On 22Dec2015 10:14, Steven D'Aprano <steve at pearwood.info> wrote:
>On Tue, 22 Dec 2015 08:44 am, Jon Ribbens wrote about mail clients that use
>the Subject line to thread messages:
>
>> Also: Thunderbird, The Bat!, Eudora, Gnus, Outlook, Outlook Express,
>> Pegasus Mail, Pine, Apple Mail, Windows Live Mail, Yahoo Mail,
>> Evolution, SquirrelMail, KMail, Windows Mail, etc.
>
>I understand that at least some of those will only use the Subject as a
>fallback when other threading information is not available. That's a
>reasonable strategy to take.
>
>As for mail clients that *always* and *exclusively* use the subject line to
>implement threading, they are horrifically broken.

A big +1 here. Even as big as +2.

>It is completely
>unreasonable to insist that people using non-broken tools must change their
>habits to support those with completely broken tools.
>
>So as far as I am concerned, if changes of subject line breaks threading for
>you, so sad, too bad. Go without threading or use a better mail client.
[...snip...]

Besides, changing the Subject line is _supposed_ to break the threading in 
these contexts: such clients clearly consider the discussion topic (subject) as 
sufficient definition of a thread, and changing the topic should imply a new 
thread to such simplistic clients.

Cheers,
Cameron Simpson <cs at zip.com.au>