pkg/60146: JetBrainsMono-ttf font uses italics by default for regular text, behaviour not observed with other fonts

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>Number:         60146
>Category:       pkg
>Synopsis:       JetBrainsMono-ttf font uses italics by default for regular text, behaviour not observed with other fonts
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 30 14:05:00 +0000 2026
>Originator:     Daniel
>Release:        NetBSD 11.0-RC2
>Organization:
>Environment:
NetBSD netbook.powerhub 11.0_RC2 NetBSD 11.0_RC2 (GENERIC) #0: Wed Mar  4 21:02:00 UTC 2026  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
When attempting to use the JetBrainsMono-ttf font with Emacs, all of the text in the entire program that isn't bold is displayed using an italic font. This is strange, as I haven't experienced this behaviour in other OS environments with the same font and Emacs config combination.

Additionally, I don't see this behaviour when swapping out JetBrainsMono for the Hack font (package name: Hack-ttf); With this font, italics are only displayed where it should usually be, such as in the buffer title.
>How-To-Repeat:
Install Emacs, JetBrainsMono-ttf, and cwm (unknown if my window manager choice has any effect on this issue).

Ensure that the font cache is correctly set up, then configure Emacs's init.el to use the font, e.g.:

(add-to-list 'default-frame-alist
             '(font . "JetBrains Mono-15")))

Then, start X and open Emacs to observe the issue.
>Fix: