Re: rmail threading

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Cc: tomas@tuxteam.de, emacs-devel@gnu.org
> Date: Mon, 30 Aug 2021 23:09:24 -0400
> 
>   > I prefer not to review a thread via a summary, because a specialized
>   > summary prevents me from easily seeing messages that don't satisfy the
>   > summary criteria.
> 
> I am not sure what this means.  A summary based on filtering will show
> some messages and not others, but how is that harmful?
> It sounds like you want two conflicting things -- what two things are they?
> 
> Could you say concretely what "prevents..,from easily seeing" means?

Once you request a summary based on filtering, the unfiltered summary
is gone.  So I can no longer quickly and conveniently look for
messages that were filtered out by scrolling the summary buffer or by
searching in it.

Suppose a message in a thread changed the subject, enough so that
neither summary by subject nor rmail-next-same-subject find it.  With
the unfiltered summary buffer, I can still look for it, e.g. by
searching for the sender or some fragment of the Subject in the
summary buffer.  With summary-by-topic, I can't do that.

> A summary in Rmail doesn't stop you from looking at messages not
> included in it.  I do that frequently.

Can you tell how do you do that?

And I have one additional question about your request to have a
summary-by-thread: is it okay to request that the user first sorts the
messages by date (C-c C-s C-d), before summarizing the thread?  If
not, then the implementation should be much more complicated, and the
resulting order of the messages in the summary could be confusing,
because messages could have arrived out of order, which happens when,
for example, the email server was temporarily off-line.  If the
messages are sorted by date/time, the order will be reasonable
(barring clock mismatches).