On Thu,  6 May 2021 at 14:57, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Augusto Stoffel <arstoffel@gmail.com>
>> Cc: stefankangas@gmail.com,  jporterbugs@gmail.com,  emacs-devel@gnu.org
>> Date: Thu, 06 May 2021 13:47:56 +0200
>> 
>> Anyway, I think we can agree that setting `line-spacing' to nil is *not*
>> analogous setting \baselineskip=0pt in TeX.
>
> I'm TeX-illiterate.  Can you explain why these two aren't analogous?
> It sounds like they are, when I read the definition of what
> \baselineskip=0pt does.

\baselineskip=0pt and (setq line-spacing nil) both mean to typeset lines
as close as possible, without overlapping bounding boxes.  But the
achieved effect is very different, because "source code typography" and
"manual typography" are very different.

I've attached a PDF where the first page uses the default \baselineskip,
the second sets it to zero.  Which one looks more like emacs -Q?