The *Summary* buffer has now a garbled line. Howver the *Article* buffer
is still doing fine.

Funny thing is, if we pipe the second article through procmail, and
enter gnus again, the newly created identical third article has an OK
*Summary* line.

Important settings:
  value of $LC_COLLATE: C
  value of $LC_CTYPE: zh_TW.UTF-8
  value of $LC_MESSAGES: C
  value of $LANG: zh_TW.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

(One also notes raw big5 enters the .overview file, but not always.)

My dot files are at https://www.jidanni.org/comp/configuration/

Anyway, sure, gnus can deal with such wacky headers fine on the first
day.

But on the second day, after totally quitting emacs and starting up
again, such headers are no longer dealt with properly, at least in the
*Summary* buffer.

Sure, "Tell the agency to stop sending illegal headers." Well, yes...