When the UI language is not the same as the page language, the "reply", "subscribe" and "unsubscribe" links are translated, but no lang/dir attributes are added to the text.
e.g. If you go to https://meta.wikimedia.org/wiki/Talk:Main_Page?uselang=de, the "reply" link will be translated to "Beantworten". If you also add a:lang(en) { background-color: pink } using the browser's developer tools, it will get a pink background, because the browser thinks the language is English.