[ Perhaps sysad...@gnu.org is the right place to report this -- if so, please bounce/forward the message and sorry for bothering. ]
I have a vague feeling that I've reported this before, some (many?) years ago. A Subject: of an email message in UTF-8 encoding but containing other than US-ASCII characters appears garbled in the thread view of a mailing list archive: https://lists.nongnu.org/archive/html/gug-bg-herd/2019-11/threads.html This makes it difficult to locate a particular message when an archived URL is needed and is also a nuisance when a new list subscriber decides to read some messages from the time before he became a list member. That's a minor annoyance probably affecting only a few lists (www.gnu.org translation teams come to mind) but it's still something worth fixing, I guess.