whither italics

[James K. Lowden]

I have two installations of emacs on different VMs. I don't understand
why one sometimes shows words in italics that the other shows
underlined.

The display is X11 via ssh on a Mac using XQuartz. The old machine has

GNU Emacs 25.1.2 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)
of 2016-12-15

Since this is /usr/local/bin/emacs, on the evidence I built it from
source a few years ago.

The new machine has

GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.14)
of 2020-03-26, modified by Debian

Perhaps a little impetuously, I configured the new machine by
copying .emacs and .emacs.d from old to new. I guess there's a font
setting whose name changed between those two versions?

With ~/.emacs loaded and the cursor at 1,1 on the first "#", I press

C-u C-x =

to describe the font for that character. That opens a window labeled
*Help*. Near the bottom of that buffer it says:

[snip]
xft:-PfEd-DejaVu Sans
Mono-normal-normal-normal-*-12-*-*-*-m-0-iso10646-1 (#x06)
...
There are text properties here:
face font-lock-comment-delimiter-face
fontified t
[pins]

On the old machine, the words "face" and "fontified" are in italics.
On the new machine, they're upright (normal) and the text of both lines
is underlined from the left edge to the last character, including
spaces.

To me, there's hardly anything in emacs more complicated than fonts.
What setting would cause the new emacs to render italics as underlined?

Probably unrelated, but also baffling, btw: on the new machine, when
emacs starts up, the initial window is just a few lines high. The same
is true for new frames from C-x 5 2. The old machine, using the same
configuration on the same display, starts out 40 lines high or so.

Many thanks.

--jkl

[James K. Lowden]