Both Emacs variants fail to do what I'd expect:

- Emacs 26 uses variable-pitch for <code> elements,
- Emacs 27+ uses the default face, which does ensure a monospace font,
  but also neutralizes any effects of enclosing elements, e.g.
    - no bold inside <strong>,
    - no italics inside <em>,
    - no blue color nor underline inside <a>.

For example, here is how Firefox 72 does it: