Hello,

I have configured Gnus to gather loose threads under a dummy root
article.  I have "%S" set in gnus-summary-dummy-line-format, and %s in
gnus-summary-line-format: my intent is to have the thread subject show
up only once, on the dummy root.

Sometimes this works:

                     ┌◈                          bug#40337: 28.0.50; Enable case-fold-search in hi-lock
    02:08            ├► Juri Linkov
    05:33            ╰► Stefan Monnier

And sometimes it doesn't:

                     ┌◈                          Re: Emacs's set-frame-size can not work well with gnome-shell?
    10:32            ├► martin rudalics          Re: Emacs's set-frame-size can not work well with gnome-shell?
    16:04            │╰► Eli Zaretskii
    10:33            ├► martin rudalics
    15:19            │╰► Dmitry Gutov
    10:33            ╰► martin rudalics

I poked at lisp/gnus/gnus-sum.el and reported this as bug#40520, where I
suggested the following patch: