I was translating the article June Almeida into Hebrew. I added two templates manually: {{כ}} and {{משמאל לימין}}.

I closed the tab, and when re-opened it, the templates were not rendered, but shown with the puzzle icons:

Notice the puzzle icons with gray text in the first line of the first paragraph and in the second line of the second paragraph. In the first paragraph nothing is supposed to be seen there, because this template adds the zero-width right to left mark. In the second paragraph, it's supposed to show the text "Sc.D." (this template wraps the text in <span dir="ltr"></span>).

I'm not sure whether it's a Visual Editor or a Content Translation bug, so tagging both.