The show-font-list command was using a custom buffer that listed font families and their corresponding short preview. In the past, the font listing would include families that could not display the show-font-pangram or, indeed, any Latin character. If it does not, then (i) it is highlighted with a different colour, (ii) it shows “No preview” instead of the pangram, and (iii) it displays the information in the Emacs default font family.