Noto Sans N Ko

Anywhere that the intent of text is to demonstrate a font, we use a "Tofu"/missing glyph fallback font. Otherwise you might think you're seeing the font you're interested in, but you're actually seeing some other font the browser picked.

Here are some reasons you might see a missing glyph:

If you use any of the fonts in your own website, you will get the normal fallback behavior, and not the Tofu/missing glyph you might see here.