Something that'll make you happy I hope: there's already a bug filed to make it possible to customize the date and time format in your journal - an use non-US formats - and I hope I'll be able to work on it soon. Unfortunately, styles bugs are sometimes connected so you have to put some on the backburner till others get fixed. And I'll stop rambling now. :)

Edit: and to answer your question, you need to add this to a theme or a user layer:

function Comment::time_display (string datefmt, string timefmt) : string {
return $this->time_display("med", $timefmt, false);
}