It seems like a bug.
I can confirm this happens on Konsole, but not on XTerm on the same machine and user-session.
Can you check bugs.kde.org for any existing report about this?
And if there aren’t any, open a new one?
My installation details:
Operating System: openSUSE Tumbleweed 20250613
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.1
Kernel Version: 6.15.2-1-default (64-bit)
Graphics Platform: X11
My language and locale environment variables:
~ $ printenv | grep -E '(LANG|LC)' | sort
LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_ADDRESS=pt_BR.UTF-8
LC_COLLATE=C.UTF-8
LC_CTYPE=en_US.UTF-8
LC_IDENTIFICATION=pt_BR.UTF-8
LC_MEASUREMENT=pt_BR.UTF-8
LC_MESSAGES=en_US.UTF-8
LC_MONETARY=pt_BR.UTF-8
LC_NAME=pt_BR.UTF-8
LC_NUMERIC=C.UTF-8
LC_PAPER=pt_BR.UTF-8
LC_RESPONSE=en_US.UTF-8
LC_TELEPHONE=pt_BR.UTF-8
LC_TIME=pt_BR.UTF-8